creation_sourcecode: // SPDX-License-Identifier: MIT
  // File: @openzeppelin/contracts/utils/math/SignedMath.sol
  
  
  // OpenZeppelin Contracts (last updated v5.0.0) (utils/math/SignedMath.sol)
  
  pragma solidity ^0.8.20;
  
  /**
   * @dev Standard signed math utilities missing in the Solidity language.
   */
  library SignedMath {
      /**
       * @dev Returns the largest of two signed numbers.
       */
      function max(int256 a, int256 b) internal pure returns (int256) {
          return a > b ? a : b;
      }
  
      /**
       * @dev Returns the smallest of two signed numbers.
       */
      function min(int256 a, int256 b) internal pure returns (int256) {
          return a < b ? a : b;
      }
  
      /**
       * @dev Returns the average of two signed numbers without overflow.
       * The result is rounded towards zero.
       */
      function average(int256 a, int256 b) internal pure returns (int256) {
          // Formula from the book "Hacker's Delight"
          int256 x = (a & b) + ((a ^ b) >> 1);
          return x + (int256(uint256(x) >> 255) & (a ^ b));
      }
  
      /**
       * @dev Returns the absolute unsigned value of a signed value.
       */
      function abs(int256 n) internal pure returns (uint256) {
          unchecked {
              // must be unchecked in order to support `n = type(int256).min`
              return uint256(n >= 0 ? n : -n);
          }
      }
  }
  
  // File: @openzeppelin/contracts/utils/math/Math.sol
  
  
  // OpenZeppelin Contracts (last updated v5.0.0) (utils/math/Math.sol)
  
  pragma solidity ^0.8.20;
  
  /**
   * @dev Standard math utilities missing in the Solidity language.
   */
  library Math {
      /**
       * @dev Muldiv operation overflow.
       */
      error MathOverflowedMulDiv();
  
      enum Rounding {
          Floor, // Toward negative infinity
          Ceil, // Toward positive infinity
          Trunc, // Toward zero
          Expand // Away from zero
      }
  
      /**
       * @dev Returns the addition of two unsigned integers, with an overflow flag.
       */
      function tryAdd(uint256 a, uint256 b) internal pure returns (bool, uint256) {
          unchecked {
              uint256 c = a + b;
              if (c < a) return (false, 0);
              return (true, c);
          }
      }
  
      /**
       * @dev Returns the subtraction of two unsigned integers, with an overflow flag.
       */
      function trySub(uint256 a, uint256 b) internal pure returns (bool, uint256) {
          unchecked {
              if (b > a) return (false, 0);
              return (true, a - b);
          }
      }
  
      /**
       * @dev Returns the multiplication of two unsigned integers, with an overflow flag.
       */
      function tryMul(uint256 a, uint256 b) internal pure returns (bool, uint256) {
          unchecked {
              // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
              // benefit is lost if 'b' is also tested.
              // See: https://github.com/OpenZeppelin/openzeppelin-contracts/pull/522
              if (a == 0) return (true, 0);
              uint256 c = a * b;
              if (c / a != b) return (false, 0);
              return (true, c);
          }
      }
  
      /**
       * @dev Returns the division of two unsigned integers, with a division by zero flag.
       */
      function tryDiv(uint256 a, uint256 b) internal pure returns (bool, uint256) {
          unchecked {
              if (b == 0) return (false, 0);
              return (true, a / b);
          }
      }
  
      /**
       * @dev Returns the remainder of dividing two unsigned integers, with a division by zero flag.
       */
      function tryMod(uint256 a, uint256 b) internal pure returns (bool, uint256) {
          unchecked {
              if (b == 0) return (false, 0);
              return (true, a % b);
          }
      }
  
      /**
       * @dev Returns the largest of two numbers.
       */
      function max(uint256 a, uint256 b) internal pure returns (uint256) {
          return a > b ? a : b;
      }
  
      /**
       * @dev Returns the smallest of two numbers.
       */
      function min(uint256 a, uint256 b) internal pure returns (uint256) {
          return a < b ? a : b;
      }
  
      /**
       * @dev Returns the average of two numbers. The result is rounded towards
       * zero.
       */
      function average(uint256 a, uint256 b) internal pure returns (uint256) {
          // (a + b) / 2 can overflow.
          return (a & b) + (a ^ b) / 2;
      }
  
      /**
       * @dev Returns the ceiling of the division of two numbers.
       *
       * This differs from standard division with `/` in that it rounds towards infinity instead
       * of rounding towards zero.
       */
      function ceilDiv(uint256 a, uint256 b) internal pure returns (uint256) {
          if (b == 0) {
              // Guarantee the same behavior as in a regular Solidity division.
              return a / b;
          }
  
          // (a + b - 1) / b can overflow on addition, so we distribute.
          return a == 0 ? 0 : (a - 1) / b + 1;
      }
  
      /**
       * @notice Calculates floor(x * y / denominator) with full precision. Throws if result overflows a uint256 or
       * denominator == 0.
       * @dev Original credit to Remco Bloemen under MIT license (https://xn--2-umb.com/21/muldiv) with further edits by
       * Uniswap Labs also under MIT license.
       */
      function mulDiv(uint256 x, uint256 y, uint256 denominator) internal pure returns (uint256 result) {
          unchecked {
              // 512-bit multiply [prod1 prod0] = x * y. Compute the product mod 2^256 and mod 2^256 - 1, then use
              // use the Chinese Remainder Theorem to reconstruct the 512 bit result. The result is stored in two 256
              // variables such that product = prod1 * 2^256 + prod0.
              uint256 prod0 = x * y; // Least significant 256 bits of the product
              uint256 prod1; // Most significant 256 bits of the product
              assembly {
                  let mm := mulmod(x, y, not(0))
                  prod1 := sub(sub(mm, prod0), lt(mm, prod0))
              }
  
              // Handle non-overflow cases, 256 by 256 division.
              if (prod1 == 0) {
                  // Solidity will revert if denominator == 0, unlike the div opcode on its own.
                  // The surrounding unchecked block does not change this fact.
                  // See https://docs.soliditylang.org/en/latest/control-structures.html#checked-or-unchecked-arithmetic.
                  return prod0 / denominator;
              }
  
              // Make sure the result is less than 2^256. Also prevents denominator == 0.
              if (denominator <= prod1) {
                  revert MathOverflowedMulDiv();
              }
  
              ///////////////////////////////////////////////
              // 512 by 256 division.
              ///////////////////////////////////////////////
  
              // Make division exact by subtracting the remainder from [prod1 prod0].
              uint256 remainder;
              assembly {
                  // Compute remainder using mulmod.
                  remainder := mulmod(x, y, denominator)
  
                  // Subtract 256 bit number from 512 bit number.
                  prod1 := sub(prod1, gt(remainder, prod0))
                  prod0 := sub(prod0, remainder)
              }
  
              // Factor powers of two out of denominator and compute largest power of two divisor of denominator.
              // Always >= 1. See https://cs.stackexchange.com/q/138556/92363.
  
              uint256 twos = denominator & (0 - denominator);
              assembly {
                  // Divide denominator by twos.
                  denominator := div(denominator, twos)
  
                  // Divide [prod1 prod0] by twos.
                  prod0 := div(prod0, twos)
  
                  // Flip twos such that it is 2^256 / twos. If twos is zero, then it becomes one.
                  twos := add(div(sub(0, twos), twos), 1)
              }
  
              // Shift in bits from prod1 into prod0.
              prod0 |= prod1 * twos;
  
              // Invert denominator mod 2^256. Now that denominator is an odd number, it has an inverse modulo 2^256 such
              // that denominator * inv = 1 mod 2^256. Compute the inverse by starting with a seed that is correct for
              // four bits. That is, denominator * inv = 1 mod 2^4.
              uint256 inverse = (3 * denominator) ^ 2;
  
              // Use the Newton-Raphson iteration to improve the precision. Thanks to Hensel's lifting lemma, this also
              // works in modular arithmetic, doubling the correct bits in each step.
              inverse *= 2 - denominator * inverse; // inverse mod 2^8
              inverse *= 2 - denominator * inverse; // inverse mod 2^16
              inverse *= 2 - denominator * inverse; // inverse mod 2^32
              inverse *= 2 - denominator * inverse; // inverse mod 2^64
              inverse *= 2 - denominator * inverse; // inverse mod 2^128
              inverse *= 2 - denominator * inverse; // inverse mod 2^256
  
              // Because the division is now exact we can divide by multiplying with the modular inverse of denominator.
              // This will give us the correct result modulo 2^256. Since the preconditions guarantee that the outcome is
              // less than 2^256, this is the final result. We don't need to compute the high bits of the result and prod1
              // is no longer required.
              result = prod0 * inverse;
              return result;
          }
      }
  
      /**
       * @notice Calculates x * y / denominator with full precision, following the selected rounding direction.
       */
      function mulDiv(uint256 x, uint256 y, uint256 denominator, Rounding rounding) internal pure returns (uint256) {
          uint256 result = mulDiv(x, y, denominator);
          if (unsignedRoundsUp(rounding) && mulmod(x, y, denominator) > 0) {
              result += 1;
          }
          return result;
      }
  
      /**
       * @dev Returns the square root of a number. If the number is not a perfect square, the value is rounded
       * towards zero.
       *
       * Inspired by Henry S. Warren, Jr.'s "Hacker's Delight" (Chapter 11).
       */
      function sqrt(uint256 a) internal pure returns (uint256) {
          if (a == 0) {
              return 0;
          }
  
          // For our first guess, we get the biggest power of 2 which is smaller than the square root of the target.
          //
          // We know that the "msb" (most significant bit) of our target number `a` is a power of 2 such that we have
          // `msb(a) <= a < 2*msb(a)`. This value can be written `msb(a)=2**k` with `k=log2(a)`.
          //
          // This can be rewritten `2**log2(a) <= a < 2**(log2(a) + 1)`
          // → `sqrt(2**k) <= sqrt(a) < sqrt(2**(k+1))`
          // → `2**(k/2) <= sqrt(a) < 2**((k+1)/2) <= 2**(k/2 + 1)`
          //
          // Consequently, `2**(log2(a) / 2)` is a good first approximation of `sqrt(a)` with at least 1 correct bit.
          uint256 result = 1 << (log2(a) >> 1);
  
          // At this point `result` is an estimation with one bit of precision. We know the true value is a uint128,
          // since it is the square root of a uint256. Newton's method converges quadratically (precision doubles at
          // every iteration). We thus need at most 7 iteration to turn our partial result with one bit of precision
          // into the expected uint128 result.
          unchecked {
              result = (result + a / result) >> 1;
              result = (result + a / result) >> 1;
              result = (result + a / result) >> 1;
              result = (result + a / result) >> 1;
              result = (result + a / result) >> 1;
              result = (result + a / result) >> 1;
              result = (result + a / result) >> 1;
              return min(result, a / result);
          }
      }
  
      /**
       * @notice Calculates sqrt(a), following the selected rounding direction.
       */
      function sqrt(uint256 a, Rounding rounding) internal pure returns (uint256) {
          unchecked {
              uint256 result = sqrt(a);
              return result + (unsignedRoundsUp(rounding) && result * result < a ? 1 : 0);
          }
      }
  
      /**
       * @dev Return the log in base 2 of a positive value rounded towards zero.
       * Returns 0 if given 0.
       */
      function log2(uint256 value) internal pure returns (uint256) {
          uint256 result = 0;
          unchecked {
              if (value >> 128 > 0) {
                  value >>= 128;
                  result += 128;
              }
              if (value >> 64 > 0) {
                  value >>= 64;
                  result += 64;
              }
              if (value >> 32 > 0) {
                  value >>= 32;
                  result += 32;
              }
              if (value >> 16 > 0) {
                  value >>= 16;
                  result += 16;
              }
              if (value >> 8 > 0) {
                  value >>= 8;
                  result += 8;
              }
              if (value >> 4 > 0) {
                  value >>= 4;
                  result += 4;
              }
              if (value >> 2 > 0) {
                  value >>= 2;
                  result += 2;
              }
              if (value >> 1 > 0) {
                  result += 1;
              }
          }
          return result;
      }
  
      /**
       * @dev Return the log in base 2, following the selected rounding direction, of a positive value.
       * Returns 0 if given 0.
       */
      function log2(uint256 value, Rounding rounding) internal pure returns (uint256) {
          unchecked {
              uint256 result = log2(value);
              return result + (unsignedRoundsUp(rounding) && 1 << result < value ? 1 : 0);
          }
      }
  
      /**
       * @dev Return the log in base 10 of a positive value rounded towards zero.
       * Returns 0 if given 0.
       */
      function log10(uint256 value) internal pure returns (uint256) {
          uint256 result = 0;
          unchecked {
              if (value >= 10 ** 64) {
                  value /= 10 ** 64;
                  result += 64;
              }
              if (value >= 10 ** 32) {
                  value /= 10 ** 32;
                  result += 32;
              }
              if (value >= 10 ** 16) {
                  value /= 10 ** 16;
                  result += 16;
              }
              if (value >= 10 ** 8) {
                  value /= 10 ** 8;
                  result += 8;
              }
              if (value >= 10 ** 4) {
                  value /= 10 ** 4;
                  result += 4;
              }
              if (value >= 10 ** 2) {
                  value /= 10 ** 2;
                  result += 2;
              }
              if (value >= 10 ** 1) {
                  result += 1;
              }
          }
          return result;
      }
  
      /**
       * @dev Return the log in base 10, following the selected rounding direction, of a positive value.
       * Returns 0 if given 0.
       */
      function log10(uint256 value, Rounding rounding) internal pure returns (uint256) {
          unchecked {
              uint256 result = log10(value);
              return result + (unsignedRoundsUp(rounding) && 10 ** result < value ? 1 : 0);
          }
      }
  
      /**
       * @dev Return the log in base 256 of a positive value rounded towards zero.
       * Returns 0 if given 0.
       *
       * Adding one to the result gives the number of pairs of hex symbols needed to represent `value` as a hex string.
       */
      function log256(uint256 value) internal pure returns (uint256) {
          uint256 result = 0;
          unchecked {
              if (value >> 128 > 0) {
                  value >>= 128;
                  result += 16;
              }
              if (value >> 64 > 0) {
                  value >>= 64;
                  result += 8;
              }
              if (value >> 32 > 0) {
                  value >>= 32;
                  result += 4;
              }
              if (value >> 16 > 0) {
                  value >>= 16;
                  result += 2;
              }
              if (value >> 8 > 0) {
                  result += 1;
              }
          }
          return result;
      }
  
      /**
       * @dev Return the log in base 256, following the selected rounding direction, of a positive value.
       * Returns 0 if given 0.
       */
      function log256(uint256 value, Rounding rounding) internal pure returns (uint256) {
          unchecked {
              uint256 result = log256(value);
              return result + (unsignedRoundsUp(rounding) && 1 << (result << 3) < value ? 1 : 0);
          }
      }
  
      /**
       * @dev Returns whether a provided rounding mode is considered rounding up for unsigned integers.
       */
      function unsignedRoundsUp(Rounding rounding) internal pure returns (bool) {
          return uint8(rounding) % 2 == 1;
      }
  }
  
  // File: @openzeppelin/contracts/utils/Strings.sol
  
  
  // OpenZeppelin Contracts (last updated v5.0.0) (utils/Strings.sol)
  
  pragma solidity ^0.8.20;
  
  
  
  /**
   * @dev String operations.
   */
  library Strings {
      bytes16 private constant HEX_DIGITS = "0123456789abcdef";
      uint8 private constant ADDRESS_LENGTH = 20;
  
      /**
       * @dev The `value` string doesn't fit in the specified `length`.
       */
      error StringsInsufficientHexLength(uint256 value, uint256 length);
  
      /**
       * @dev Converts a `uint256` to its ASCII `string` decimal representation.
       */
      function toString(uint256 value) internal pure returns (string memory) {
          unchecked {
              uint256 length = Math.log10(value) + 1;
              string memory buffer = new string(length);
              uint256 ptr;
              /// @solidity memory-safe-assembly
              assembly {
                  ptr := add(buffer, add(32, length))
              }
              while (true) {
                  ptr--;
                  /// @solidity memory-safe-assembly
                  assembly {
                      mstore8(ptr, byte(mod(value, 10), HEX_DIGITS))
                  }
                  value /= 10;
                  if (value == 0) break;
              }
              return buffer;
          }
      }
  
      /**
       * @dev Converts a `int256` to its ASCII `string` decimal representation.
       */
      function toStringSigned(int256 value) internal pure returns (string memory) {
          return string.concat(value < 0 ? "-" : "", toString(SignedMath.abs(value)));
      }
  
      /**
       * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation.
       */
      function toHexString(uint256 value) internal pure returns (string memory) {
          unchecked {
              return toHexString(value, Math.log256(value) + 1);
          }
      }
  
      /**
       * @dev Converts a `uint256` to its ASCII `string` hexadecimal representation with fixed length.
       */
      function toHexString(uint256 value, uint256 length) internal pure returns (string memory) {
          uint256 localValue = value;
          bytes memory buffer = new bytes(2 * length + 2);
          buffer[0] = "0";
          buffer[1] = "x";
          for (uint256 i = 2 * length + 1; i > 1; --i) {
              buffer[i] = HEX_DIGITS[localValue & 0xf];
              localValue >>= 4;
          }
          if (localValue != 0) {
              revert StringsInsufficientHexLength(value, length);
          }
          return string(buffer);
      }
  
      /**
       * @dev Converts an `address` with fixed length of 20 bytes to its not checksummed ASCII `string` hexadecimal
       * representation.
       */
      function toHexString(address addr) internal pure returns (string memory) {
          return toHexString(uint256(uint160(addr)), ADDRESS_LENGTH);
      }
  
      /**
       * @dev Returns true if the two strings are equal.
       */
      function equal(string memory a, string memory b) internal pure returns (bool) {
          return bytes(a).length == bytes(b).length && keccak256(bytes(a)) == keccak256(bytes(b));
      }
  }
  
  // File: @openzeppelin/contracts/security/ReentrancyGuard.sol
  
  
  // OpenZeppelin Contracts (last updated v4.9.0) (security/ReentrancyGuard.sol)
  
  pragma solidity ^0.8.0;
  
  /**
   * @dev Contract module that helps prevent reentrant calls to a function.
   *
   * Inheriting from `ReentrancyGuard` will make the {nonReentrant} modifier
   * available, which can be applied to functions to make sure there are no nested
   * (reentrant) calls to them.
   *
   * Note that because there is a single `nonReentrant` guard, functions marked as
   * `nonReentrant` may not call one another. This can be worked around by making
   * those functions `private`, and then adding `external` `nonReentrant` entry
   * points to them.
   *
   * TIP: If you would like to learn more about reentrancy and alternative ways
   * to protect against it, check out our blog post
   * https://blog.openzeppelin.com/reentrancy-after-istanbul/[Reentrancy After Istanbul].
   */
  abstract contract ReentrancyGuard {
      // Booleans are more expensive than uint256 or any type that takes up a full
      // word because each write operation emits an extra SLOAD to first read the
      // slot's contents, replace the bits taken up by the boolean, and then write
      // back. This is the compiler's defense against contract upgrades and
      // pointer aliasing, and it cannot be disabled.
  
      // The values being non-zero value makes deployment a bit more expensive,
      // but in exchange the refund on every call to nonReentrant will be lower in
      // amount. Since refunds are capped to a percentage of the total
      // transaction's gas, it is best to keep them low in cases like this one, to
      // increase the likelihood of the full refund coming into effect.
      uint256 private constant _NOT_ENTERED = 1;
      uint256 private constant _ENTERED = 2;
  
      uint256 private _status;
  
      constructor() {
          _status = _NOT_ENTERED;
      }
  
      /**
       * @dev Prevents a contract from calling itself, directly or indirectly.
       * Calling a `nonReentrant` function from another `nonReentrant`
       * function is not supported. It is possible to prevent this from happening
       * by making the `nonReentrant` function external, and making it call a
       * `private` function that does the actual work.
       */
      modifier nonReentrant() {
          _nonReentrantBefore();
          _;
          _nonReentrantAfter();
      }
  
      function _nonReentrantBefore() private {
          // On the first call to nonReentrant, _status will be _NOT_ENTERED
          require(_status != _ENTERED, "ReentrancyGuard: reentrant call");
  
          // Any calls to nonReentrant after this point will fail
          _status = _ENTERED;
      }
  
      function _nonReentrantAfter() private {
          // By storing the original value once again, a refund is triggered (see
          // https://eips.ethereum.org/EIPS/eip-2200)
          _status = _NOT_ENTERED;
      }
  
      /**
       * @dev Returns true if the reentrancy guard is currently set to "entered", which indicates there is a
       * `nonReentrant` function in the call stack.
       */
      function _reentrancyGuardEntered() internal view returns (bool) {
          return _status == _ENTERED;
      }
  }
  
  // File: @openzeppelin/contracts/utils/Context.sol
  
  
  // OpenZeppelin Contracts (last updated v5.0.1) (utils/Context.sol)
  
  pragma solidity ^0.8.20;
  
  /**
   * @dev Provides information about the current execution context, including the
   * sender of the transaction and its data. While these are generally available
   * via msg.sender and msg.data, they should not be accessed in such a direct
   * manner, since when dealing with meta-transactions the account sending and
   * paying for execution may not be the actual sender (as far as an application
   * is concerned).
   *
   * This contract is only required for intermediate, library-like contracts.
   */
  abstract contract Context {
      function _msgSender() internal view virtual returns (address) {
          return msg.sender;
      }
  
      function _msgData() internal view virtual returns (bytes calldata) {
          return msg.data;
      }
  
      function _contextSuffixLength() internal view virtual returns (uint256) {
          return 0;
      }
  }
  
  // File: @openzeppelin/contracts/access/Ownable.sol
  
  
  // OpenZeppelin Contracts (last updated v5.0.0) (access/Ownable.sol)
  
  pragma solidity ^0.8.20;
  
  
  /**
   * @dev Contract module which provides a basic access control mechanism, where
   * there is an account (an owner) that can be granted exclusive access to
   * specific functions.
   *
   * The initial owner is set to the address provided by the deployer. This can
   * later be changed with {transferOwnership}.
   *
   * This module is used through inheritance. It will make available the modifier
   * `onlyOwner`, which can be applied to your functions to restrict their use to
   * the owner.
   */
  abstract contract Ownable is Context {
      address private _owner;
  
      /**
       * @dev The caller account is not authorized to perform an operation.
       */
      error OwnableUnauthorizedAccount(address account);
  
      /**
       * @dev The owner is not a valid owner account. (eg. `address(0)`)
       */
      error OwnableInvalidOwner(address owner);
  
      event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);
  
      /**
       * @dev Initializes the contract setting the address provided by the deployer as the initial owner.
       */
      constructor(address initialOwner) {
          if (initialOwner == address(0)) {
              revert OwnableInvalidOwner(address(0));
          }
          _transferOwnership(initialOwner);
      }
  
      /**
       * @dev Throws if called by any account other than the owner.
       */
      modifier onlyOwner() {
          _checkOwner();
          _;
      }
  
      /**
       * @dev Returns the address of the current owner.
       */
      function owner() public view virtual returns (address) {
          return _owner;
      }
  
      /**
       * @dev Throws if the sender is not the owner.
       */
      function _checkOwner() internal view virtual {
          if (owner() != _msgSender()) {
              revert OwnableUnauthorizedAccount(_msgSender());
          }
      }
  
      /**
       * @dev Leaves the contract without owner. It will not be possible to call
       * `onlyOwner` functions. Can only be called by the current owner.
       *
       * NOTE: Renouncing ownership will leave the contract without an owner,
       * thereby disabling any functionality that is only available to the owner.
       */
      function renounceOwnership() public virtual onlyOwner {
          _transferOwnership(address(0));
      }
  
      /**
       * @dev Transfers ownership of the contract to a new account (`newOwner`).
       * Can only be called by the current owner.
       */
      function transferOwnership(address newOwner) public virtual onlyOwner {
          if (newOwner == address(0)) {
              revert OwnableInvalidOwner(address(0));
          }
          _transferOwnership(newOwner);
      }
  
      /**
       * @dev Transfers ownership of the contract to a new account (`newOwner`).
       * Internal function without access restriction.
       */
      function _transferOwnership(address newOwner) internal virtual {
          address oldOwner = _owner;
          _owner = newOwner;
          emit OwnershipTransferred(oldOwner, newOwner);
      }
  }
  
  // File: erc721a/contracts/IERC721A.sol
  
  
  // ERC721A Contracts v4.3.0
  // Creator: Chiru Labs
  
  pragma solidity ^0.8.4;
  
  /**
   * @dev Interface of ERC721A.
   */
  interface IERC721A {
      /**
       * The caller must own the token or be an approved operator.
       */
      error ApprovalCallerNotOwnerNorApproved();
  
      /**
       * The token does not exist.
       */
      error ApprovalQueryForNonexistentToken();
  
      /**
       * Cannot query the balance for the zero address.
       */
      error BalanceQueryForZeroAddress();
  
      /**
       * Cannot mint to the zero address.
       */
      error MintToZeroAddress();
  
      /**
       * The quantity of tokens minted must be more than zero.
       */
      error MintZeroQuantity();
  
      /**
       * The token does not exist.
       */
      error OwnerQueryForNonexistentToken();
  
      /**
       * The caller must own the token or be an approved operator.
       */
      error TransferCallerNotOwnerNorApproved();
  
      /**
       * The token must be owned by `from`.
       */
      error TransferFromIncorrectOwner();
  
      /**
       * Cannot safely transfer to a contract that does not implement the
       * ERC721Receiver interface.
       */
      error TransferToNonERC721ReceiverImplementer();
  
      /**
       * Cannot transfer to the zero address.
       */
      error TransferToZeroAddress();
  
      /**
       * The token does not exist.
       */
      error URIQueryForNonexistentToken();
  
      /**
       * The `quantity` minted with ERC2309 exceeds the safety limit.
       */
      error MintERC2309QuantityExceedsLimit();
  
      /**
       * The `extraData` cannot be set on an unintialized ownership slot.
       */
      error OwnershipNotInitializedForExtraData();
  
      /**
       * `_sequentialUpTo()` must be greater than `_startTokenId()`.
       */
      error SequentialUpToTooSmall();
  
      /**
       * The `tokenId` of a sequential mint exceeds `_sequentialUpTo()`.
       */
      error SequentialMintExceedsLimit();
  
      /**
       * Spot minting requires a `tokenId` greater than `_sequentialUpTo()`.
       */
      error SpotMintTokenIdTooSmall();
  
      /**
       * Cannot mint over a token that already exists.
       */
      error TokenAlreadyExists();
  
      /**
       * The feature is not compatible with spot mints.
       */
      error NotCompatibleWithSpotMints();
  
      // =============================================================
      //                            STRUCTS
      // =============================================================
  
      struct TokenOwnership {
          // The address of the owner.
          address addr;
          // Stores the start time of ownership with minimal overhead for tokenomics.
          uint64 startTimestamp;
          // Whether the token has been burned.
          bool burned;
          // Arbitrary data similar to `startTimestamp` that can be set via {_extraData}.
          uint24 extraData;
      }
  
      // =============================================================
      //                         TOKEN COUNTERS
      // =============================================================
  
      /**
       * @dev Returns the total number of tokens in existence.
       * Burned tokens will reduce the count.
       * To get the total number of tokens minted, please see {_totalMinted}.
       */
      function totalSupply() external view returns (uint256);
  
      // =============================================================
      //                            IERC165
      // =============================================================
  
      /**
       * @dev Returns true if this contract implements the interface defined by
       * `interfaceId`. See the corresponding
       * [EIP section](https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified)
       * to learn more about how these ids are created.
       *
       * This function call must use less than 30000 gas.
       */
      function supportsInterface(bytes4 interfaceId) external view returns (bool);
  
      // =============================================================
      //                            IERC721
      // =============================================================
  
      /**
       * @dev Emitted when `tokenId` token is transferred from `from` to `to`.
       */
      event Transfer(address indexed from, address indexed to, uint256 indexed tokenId);
  
      /**
       * @dev Emitted when `owner` enables `approved` to manage the `tokenId` token.
       */
      event Approval(address indexed owner, address indexed approved, uint256 indexed tokenId);
  
      /**
       * @dev Emitted when `owner` enables or disables
       * (`approved`) `operator` to manage all of its assets.
       */
      event ApprovalForAll(address indexed owner, address indexed operator, bool approved);
  
      /**
       * @dev Returns the number of tokens in `owner`'s account.
       */
      function balanceOf(address owner) external view returns (uint256 balance);
  
      /**
       * @dev Returns the owner of the `tokenId` token.
       *
       * Requirements:
       *
       * - `tokenId` must exist.
       */
      function ownerOf(uint256 tokenId) external view returns (address owner);
  
      /**
       * @dev Safely transfers `tokenId` token from `from` to `to`,
       * checking first that contract recipients are aware of the ERC721 protocol
       * to prevent tokens from being forever locked.
       *
       * Requirements:
       *
       * - `from` cannot be the zero address.
       * - `to` cannot be the zero address.
       * - `tokenId` token must exist and be owned by `from`.
       * - If the caller is not `from`, it must be have been allowed to move
       * this token by either {approve} or {setApprovalForAll}.
       * - If `to` refers to a smart contract, it must implement
       * {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
       *
       * Emits a {Transfer} event.
       */
      function safeTransferFrom(
          address from,
          address to,
          uint256 tokenId,
          bytes calldata data
      ) external payable;
  
      /**
       * @dev Equivalent to `safeTransferFrom(from, to, tokenId, '')`.
       */
      function safeTransferFrom(
          address from,
          address to,
          uint256 tokenId
      ) external payable;
  
      /**
       * @dev Transfers `tokenId` from `from` to `to`.
       *
       * WARNING: Usage of this method is discouraged, use {safeTransferFrom}
       * whenever possible.
       *
       * Requirements:
       *
       * - `from` cannot be the zero address.
       * - `to` cannot be the zero address.
       * - `tokenId` token must be owned by `from`.
       * - If the caller is not `from`, it must be approved to move this token
       * by either {approve} or {setApprovalForAll}.
       *
       * Emits a {Transfer} event.
       */
      function transferFrom(
          address from,
          address to,
          uint256 tokenId
      ) external payable;
  
      /**
       * @dev Gives permission to `to` to transfer `tokenId` token to another account.
       * The approval is cleared when the token is transferred.
       *
       * Only a single account can be approved at a time, so approving the
       * zero address clears previous approvals.
       *
       * Requirements:
       *
       * - The caller must own the token or be an approved operator.
       * - `tokenId` must exist.
       *
       * Emits an {Approval} event.
       */
      function approve(address to, uint256 tokenId) external payable;
  
      /**
       * @dev Approve or remove `operator` as an operator for the caller.
       * Operators can call {transferFrom} or {safeTransferFrom}
       * for any token owned by the caller.
       *
       * Requirements:
       *
       * - The `operator` cannot be the caller.
       *
       * Emits an {ApprovalForAll} event.
       */
      function setApprovalForAll(address operator, bool _approved) external;
  
      /**
       * @dev Returns the account approved for `tokenId` token.
       *
       * Requirements:
       *
       * - `tokenId` must exist.
       */
      function getApproved(uint256 tokenId) external view returns (address operator);
  
      /**
       * @dev Returns if the `operator` is allowed to manage all of the assets of `owner`.
       *
       * See {setApprovalForAll}.
       */
      function isApprovedForAll(address owner, address operator) external view returns (bool);
  
      // =============================================================
      //                        IERC721Metadata
      // =============================================================
  
      /**
       * @dev Returns the token collection name.
       */
      function name() external view returns (string memory);
  
      /**
       * @dev Returns the token collection symbol.
       */
      function symbol() external view returns (string memory);
  
      /**
       * @dev Returns the Uniform Resource Identifier (URI) for `tokenId` token.
       */
      function tokenURI(uint256 tokenId) external view returns (string memory);
  
      // =============================================================
      //                           IERC2309
      // =============================================================
  
      /**
       * @dev Emitted when tokens in `fromTokenId` to `toTokenId`
       * (inclusive) is transferred from `from` to `to`, as defined in the
       * [ERC2309](https://eips.ethereum.org/EIPS/eip-2309) standard.
       *
       * See {_mintERC2309} for more details.
       */
      event ConsecutiveTransfer(uint256 indexed fromTokenId, uint256 toTokenId, address indexed from, address indexed to);
  }
  
  // File: erc721a/contracts/ERC721A.sol
  
  
  // ERC721A Contracts v4.3.0
  // Creator: Chiru Labs
  
  pragma solidity ^0.8.4;
  
  
  /**
   * @dev Interface of ERC721 token receiver.
   */
  interface ERC721A__IERC721Receiver {
      function onERC721Received(
          address operator,
          address from,
          uint256 tokenId,
          bytes calldata data
      ) external returns (bytes4);
  }
  
  /**
   * @title ERC721A
   *
   * @dev Implementation of the [ERC721](https://eips.ethereum.org/EIPS/eip-721)
   * Non-Fungible Token Standard, including the Metadata extension.
   * Optimized for lower gas during batch mints.
   *
   * Token IDs are minted in sequential order (e.g. 0, 1, 2, 3, ...)
   * starting from `_startTokenId()`.
   *
   * The `_sequentialUpTo()` function can be overriden to enable spot mints
   * (i.e. non-consecutive mints) for `tokenId`s greater than `_sequentialUpTo()`.
   *
   * Assumptions:
   *
   * - An owner cannot have more than 2**64 - 1 (max value of uint64) of supply.
   * - The maximum token ID cannot exceed 2**256 - 1 (max value of uint256).
   */
  contract ERC721A is IERC721A {
      // Bypass for a `--via-ir` bug (https://github.com/chiru-labs/ERC721A/pull/364).
      struct TokenApprovalRef {
          address value;
      }
  
      // =============================================================
      //                           CONSTANTS
      // =============================================================
  
      // Mask of an entry in packed address data.
      uint256 private constant _BITMASK_ADDRESS_DATA_ENTRY = (1 << 64) - 1;
  
      // The bit position of `numberMinted` in packed address data.
      uint256 private constant _BITPOS_NUMBER_MINTED = 64;
  
      // The bit position of `numberBurned` in packed address data.
      uint256 private constant _BITPOS_NUMBER_BURNED = 128;
  
      // The bit position of `aux` in packed address data.
      uint256 private constant _BITPOS_AUX = 192;
  
      // Mask of all 256 bits in packed address data except the 64 bits for `aux`.
      uint256 private constant _BITMASK_AUX_COMPLEMENT = (1 << 192) - 1;
  
      // The bit position of `startTimestamp` in packed ownership.
      uint256 private constant _BITPOS_START_TIMESTAMP = 160;
  
      // The bit mask of the `burned` bit in packed ownership.
      uint256 private constant _BITMASK_BURNED = 1 << 224;
  
      // The bit position of the `nextInitialized` bit in packed ownership.
      uint256 private constant _BITPOS_NEXT_INITIALIZED = 225;
  
      // The bit mask of the `nextInitialized` bit in packed ownership.
      uint256 private constant _BITMASK_NEXT_INITIALIZED = 1 << 225;
  
      // The bit position of `extraData` in packed ownership.
      uint256 private constant _BITPOS_EXTRA_DATA = 232;
  
      // Mask of all 256 bits in a packed ownership except the 24 bits for `extraData`.
      uint256 private constant _BITMASK_EXTRA_DATA_COMPLEMENT = (1 << 232) - 1;
  
      // The mask of the lower 160 bits for addresses.
      uint256 private constant _BITMASK_ADDRESS = (1 << 160) - 1;
  
      // The maximum `quantity` that can be minted with {_mintERC2309}.
      // This limit is to prevent overflows on the address data entries.
      // For a limit of 5000, a total of 3.689e15 calls to {_mintERC2309}
      // is required to cause an overflow, which is unrealistic.
      uint256 private constant _MAX_MINT_ERC2309_QUANTITY_LIMIT = 5000;
  
      // The `Transfer` event signature is given by:
      // `keccak256(bytes("Transfer(address,address,uint256)"))`.
      bytes32 private constant _TRANSFER_EVENT_SIGNATURE =
          0xddf252ad1be2c89b69c2b068fc378daa952ba7f163c4a11628f55a4df523b3ef;
  
      // =============================================================
      //                            STORAGE
      // =============================================================
  
      // The next token ID to be minted.
      uint256 private _currentIndex;
  
      // The number of tokens burned.
      uint256 private _burnCounter;
  
      // Token name
      string private _name;
  
      // Token symbol
      string private _symbol;
  
      // Mapping from token ID to ownership details
      // An empty struct value does not necessarily mean the token is unowned.
      // See {_packedOwnershipOf} implementation for details.
      //
      // Bits Layout:
      // - [0..159]   `addr`
      // - [160..223] `startTimestamp`
      // - [224]      `burned`
      // - [225]      `nextInitialized`
      // - [232..255] `extraData`
      mapping(uint256 => uint256) private _packedOwnerships;
  
      // Mapping owner address to address data.
      //
      // Bits Layout:
      // - [0..63]    `balance`
      // - [64..127]  `numberMinted`
      // - [128..191] `numberBurned`
      // - [192..255] `aux`
      mapping(address => uint256) private _packedAddressData;
  
      // Mapping from token ID to approved address.
      mapping(uint256 => TokenApprovalRef) private _tokenApprovals;
  
      // Mapping from owner to operator approvals
      mapping(address => mapping(address => bool)) private _operatorApprovals;
  
      // The amount of tokens minted above `_sequentialUpTo()`.
      // We call these spot mints (i.e. non-sequential mints).
      uint256 private _spotMinted;
  
      // =============================================================
      //                          CONSTRUCTOR
      // =============================================================
  
      constructor(string memory name_, string memory symbol_) {
          _name = name_;
          _symbol = symbol_;
          _currentIndex = _startTokenId();
  
          if (_sequentialUpTo() < _startTokenId()) _revert(SequentialUpToTooSmall.selector);
      }
  
      // =============================================================
      //                   TOKEN COUNTING OPERATIONS
      // =============================================================
  
      /**
       * @dev Returns the starting token ID for sequential mints.
       *
       * Override this function to change the starting token ID for sequential mints.
       *
       * Note: The value returned must never change after any tokens have been minted.
       */
      function _startTokenId() internal view virtual returns (uint256) {
          return 0;
      }
  
      /**
       * @dev Returns the maximum token ID (inclusive) for sequential mints.
       *
       * Override this function to return a value less than 2**256 - 1,
       * but greater than `_startTokenId()`, to enable spot (non-sequential) mints.
       *
       * Note: The value returned must never change after any tokens have been minted.
       */
      function _sequentialUpTo() internal view virtual returns (uint256) {
          return type(uint256).max;
      }
  
      /**
       * @dev Returns the next token ID to be minted.
       */
      function _nextTokenId() internal view virtual returns (uint256) {
          return _currentIndex;
      }
  
      /**
       * @dev Returns the total number of tokens in existence.
       * Burned tokens will reduce the count.
       * To get the total number of tokens minted, please see {_totalMinted}.
       */
      function totalSupply() public view virtual override returns (uint256 result) {
          // Counter underflow is impossible as `_burnCounter` cannot be incremented
          // more than `_currentIndex + _spotMinted - _startTokenId()` times.
          unchecked {
              // With spot minting, the intermediate `result` can be temporarily negative,
              // and the computation must be unchecked.
              result = _currentIndex - _burnCounter - _startTokenId();
              if (_sequentialUpTo() != type(uint256).max) result += _spotMinted;
          }
      }
  
      /**
       * @dev Returns the total amount of tokens minted in the contract.
       */
      function _totalMinted() internal view virtual returns (uint256 result) {
          // Counter underflow is impossible as `_currentIndex` does not decrement,
          // and it is initialized to `_startTokenId()`.
          unchecked {
              result = _currentIndex - _startTokenId();
              if (_sequentialUpTo() != type(uint256).max) result += _spotMinted;
          }
      }
  
      /**
       * @dev Returns the total number of tokens burned.
       */
      function _totalBurned() internal view virtual returns (uint256) {
          return _burnCounter;
      }
  
      /**
       * @dev Returns the total number of tokens that are spot-minted.
       */
      function _totalSpotMinted() internal view virtual returns (uint256) {
          return _spotMinted;
      }
  
      // =============================================================
      //                    ADDRESS DATA OPERATIONS
      // =============================================================
  
      /**
       * @dev Returns the number of tokens in `owner`'s account.
       */
      function balanceOf(address owner) public view virtual override returns (uint256) {
          if (owner == address(0)) _revert(BalanceQueryForZeroAddress.selector);
          return _packedAddressData[owner] & _BITMASK_ADDRESS_DATA_ENTRY;
      }
  
      /**
       * Returns the number of tokens minted by `owner`.
       */
      function _numberMinted(address owner) internal view returns (uint256) {
          return (_packedAddressData[owner] >> _BITPOS_NUMBER_MINTED) & _BITMASK_ADDRESS_DATA_ENTRY;
      }
  
      /**
       * Returns the number of tokens burned by or on behalf of `owner`.
       */
      function _numberBurned(address owner) internal view returns (uint256) {
          return (_packedAddressData[owner] >> _BITPOS_NUMBER_BURNED) & _BITMASK_ADDRESS_DATA_ENTRY;
      }
  
      /**
       * Returns the auxiliary data for `owner`. (e.g. number of whitelist mint slots used).
       */
      function _getAux(address owner) internal view returns (uint64) {
          return uint64(_packedAddressData[owner] >> _BITPOS_AUX);
      }
  
      /**
       * Sets the auxiliary data for `owner`. (e.g. number of whitelist mint slots used).
       * If there are multiple variables, please pack them into a uint64.
       */
      function _setAux(address owner, uint64 aux) internal virtual {
          uint256 packed = _packedAddressData[owner];
          uint256 auxCasted;
          // Cast `aux` with assembly to avoid redundant masking.
          assembly {
              auxCasted := aux
          }
          packed = (packed & _BITMASK_AUX_COMPLEMENT) | (auxCasted << _BITPOS_AUX);
          _packedAddressData[owner] = packed;
      }
  
      // =============================================================
      //                            IERC165
      // =============================================================
  
      /**
       * @dev Returns true if this contract implements the interface defined by
       * `interfaceId`. See the corresponding
       * [EIP section](https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified)
       * to learn more about how these ids are created.
       *
       * This function call must use less than 30000 gas.
       */
      function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
          // The interface IDs are constants representing the first 4 bytes
          // of the XOR of all function selectors in the interface.
          // See: [ERC165](https://eips.ethereum.org/EIPS/eip-165)
          // (e.g. `bytes4(i.functionA.selector ^ i.functionB.selector ^ ...)`)
          return
              interfaceId == 0x01ffc9a7 || // ERC165 interface ID for ERC165.
              interfaceId == 0x80ac58cd || // ERC165 interface ID for ERC721.
              interfaceId == 0x5b5e139f; // ERC165 interface ID for ERC721Metadata.
      }
  
      // =============================================================
      //                        IERC721Metadata
      // =============================================================
  
      /**
       * @dev Returns the token collection name.
       */
      function name() public view virtual override returns (string memory) {
          return _name;
      }
  
      /**
       * @dev Returns the token collection symbol.
       */
      function symbol() public view virtual override returns (string memory) {
          return _symbol;
      }
  
      /**
       * @dev Returns the Uniform Resource Identifier (URI) for `tokenId` token.
       */
      function tokenURI(uint256 tokenId) public view virtual override returns (string memory) {
          if (!_exists(tokenId)) _revert(URIQueryForNonexistentToken.selector);
  
          string memory baseURI = _baseURI();
          return bytes(baseURI).length != 0 ? string(abi.encodePacked(baseURI, _toString(tokenId))) : '';
      }
  
      /**
       * @dev Base URI for computing {tokenURI}. If set, the resulting URI for each
       * token will be the concatenation of the `baseURI` and the `tokenId`. Empty
       * by default, it can be overridden in child contracts.
       */
      function _baseURI() internal view virtual returns (string memory) {
          return '';
      }
  
      // =============================================================
      //                     OWNERSHIPS OPERATIONS
      // =============================================================
  
      /**
       * @dev Returns the owner of the `tokenId` token.
       *
       * Requirements:
       *
       * - `tokenId` must exist.
       */
      function ownerOf(uint256 tokenId) public view virtual override returns (address) {
          return address(uint160(_packedOwnershipOf(tokenId)));
      }
  
      /**
       * @dev Gas spent here starts off proportional to the maximum mint batch size.
       * It gradually moves to O(1) as tokens get transferred around over time.
       */
      function _ownershipOf(uint256 tokenId) internal view virtual returns (TokenOwnership memory) {
          return _unpackedOwnership(_packedOwnershipOf(tokenId));
      }
  
      /**
       * @dev Returns the unpacked `TokenOwnership` struct at `index`.
       */
      function _ownershipAt(uint256 index) internal view virtual returns (TokenOwnership memory) {
          return _unpackedOwnership(_packedOwnerships[index]);
      }
  
      /**
       * @dev Returns whether the ownership slot at `index` is initialized.
       * An uninitialized slot does not necessarily mean that the slot has no owner.
       */
      function _ownershipIsInitialized(uint256 index) internal view virtual returns (bool) {
          return _packedOwnerships[index] != 0;
      }
  
      /**
       * @dev Initializes the ownership slot minted at `index` for efficiency purposes.
       */
      function _initializeOwnershipAt(uint256 index) internal virtual {
          if (_packedOwnerships[index] == 0) {
              _packedOwnerships[index] = _packedOwnershipOf(index);
          }
      }
  
      /**
       * @dev Returns the packed ownership data of `tokenId`.
       */
      function _packedOwnershipOf(uint256 tokenId) private view returns (uint256 packed) {
          if (_startTokenId() <= tokenId) {
              packed = _packedOwnerships[tokenId];
  
              if (tokenId > _sequentialUpTo()) {
                  if (_packedOwnershipExists(packed)) return packed;
                  _revert(OwnerQueryForNonexistentToken.selector);
              }
  
              // If the data at the starting slot does not exist, start the scan.
              if (packed == 0) {
                  if (tokenId >= _currentIndex) _revert(OwnerQueryForNonexistentToken.selector);
                  // Invariant:
                  // There will always be an initialized ownership slot
                  // (i.e. `ownership.addr != address(0) && ownership.burned == false`)
                  // before an unintialized ownership slot
                  // (i.e. `ownership.addr == address(0) && ownership.burned == false`)
                  // Hence, `tokenId` will not underflow.
                  //
                  // We can directly compare the packed value.
                  // If the address is zero, packed will be zero.
                  for (;;) {
                      unchecked {
                          packed = _packedOwnerships[--tokenId];
                      }
                      if (packed == 0) continue;
                      if (packed & _BITMASK_BURNED == 0) return packed;
                      // Otherwise, the token is burned, and we must revert.
                      // This handles the case of batch burned tokens, where only the burned bit
                      // of the starting slot is set, and remaining slots are left uninitialized.
                      _revert(OwnerQueryForNonexistentToken.selector);
                  }
              }
              // Otherwise, the data exists and we can skip the scan.
              // This is possible because we have already achieved the target condition.
              // This saves 2143 gas on transfers of initialized tokens.
              // If the token is not burned, return `packed`. Otherwise, revert.
              if (packed & _BITMASK_BURNED == 0) return packed;
          }
          _revert(OwnerQueryForNonexistentToken.selector);
      }
  
      /**
       * @dev Returns the unpacked `TokenOwnership` struct from `packed`.
       */
      function _unpackedOwnership(uint256 packed) private pure returns (TokenOwnership memory ownership) {
          ownership.addr = address(uint160(packed));
          ownership.startTimestamp = uint64(packed >> _BITPOS_START_TIMESTAMP);
          ownership.burned = packed & _BITMASK_BURNED != 0;
          ownership.extraData = uint24(packed >> _BITPOS_EXTRA_DATA);
      }
  
      /**
       * @dev Packs ownership data into a single uint256.
       */
      function _packOwnershipData(address owner, uint256 flags) private view returns (uint256 result) {
          assembly {
              // Mask `owner` to the lower 160 bits, in case the upper bits somehow aren't clean.
              owner := and(owner, _BITMASK_ADDRESS)
              // `owner | (block.timestamp << _BITPOS_START_TIMESTAMP) | flags`.
              result := or(owner, or(shl(_BITPOS_START_TIMESTAMP, timestamp()), flags))
          }
      }
  
      /**
       * @dev Returns the `nextInitialized` flag set if `quantity` equals 1.
       */
      function _nextInitializedFlag(uint256 quantity) private pure returns (uint256 result) {
          // For branchless setting of the `nextInitialized` flag.
          assembly {
              // `(quantity == 1) << _BITPOS_NEXT_INITIALIZED`.
              result := shl(_BITPOS_NEXT_INITIALIZED, eq(quantity, 1))
          }
      }
  
      // =============================================================
      //                      APPROVAL OPERATIONS
      // =============================================================
  
      /**
       * @dev Gives permission to `to` to transfer `tokenId` token to another account. See {ERC721A-_approve}.
       *
       * Requirements:
       *
       * - The caller must own the token or be an approved operator.
       */
      function approve(address to, uint256 tokenId) public payable virtual override {
          _approve(to, tokenId, true);
      }
  
      /**
       * @dev Returns the account approved for `tokenId` token.
       *
       * Requirements:
       *
       * - `tokenId` must exist.
       */
      function getApproved(uint256 tokenId) public view virtual override returns (address) {
          if (!_exists(tokenId)) _revert(ApprovalQueryForNonexistentToken.selector);
  
          return _tokenApprovals[tokenId].value;
      }
  
      /**
       * @dev Approve or remove `operator` as an operator for the caller.
       * Operators can call {transferFrom} or {safeTransferFrom}
       * for any token owned by the caller.
       *
       * Requirements:
       *
       * - The `operator` cannot be the caller.
       *
       * Emits an {ApprovalForAll} event.
       */
      function setApprovalForAll(address operator, bool approved) public virtual override {
          _operatorApprovals[_msgSenderERC721A()][operator] = approved;
          emit ApprovalForAll(_msgSenderERC721A(), operator, approved);
      }
  
      /**
       * @dev Returns if the `operator` is allowed to manage all of the assets of `owner`.
       *
       * See {setApprovalForAll}.
       */
      function isApprovedForAll(address owner, address operator) public view virtual override returns (bool) {
          return _operatorApprovals[owner][operator];
      }
  
      /**
       * @dev Returns whether `tokenId` exists.
       *
       * Tokens can be managed by their owner or approved accounts via {approve} or {setApprovalForAll}.
       *
       * Tokens start existing when they are minted. See {_mint}.
       */
      function _exists(uint256 tokenId) internal view virtual returns (bool result) {
          if (_startTokenId() <= tokenId) {
              if (tokenId > _sequentialUpTo()) return _packedOwnershipExists(_packedOwnerships[tokenId]);
  
              if (tokenId < _currentIndex) {
                  uint256 packed;
                  while ((packed = _packedOwnerships[tokenId]) == 0) --tokenId;
                  result = packed & _BITMASK_BURNED == 0;
              }
          }
      }
  
      /**
       * @dev Returns whether `packed` represents a token that exists.
       */
      function _packedOwnershipExists(uint256 packed) private pure returns (bool result) {
          assembly {
              // The following is equivalent to `owner != address(0) && burned == false`.
              // Symbolically tested.
              result := gt(and(packed, _BITMASK_ADDRESS), and(packed, _BITMASK_BURNED))
          }
      }
  
      /**
       * @dev Returns whether `msgSender` is equal to `approvedAddress` or `owner`.
       */
      function _isSenderApprovedOrOwner(
          address approvedAddress,
          address owner,
          address msgSender
      ) private pure returns (bool result) {
          assembly {
              // Mask `owner` to the lower 160 bits, in case the upper bits somehow aren't clean.
              owner := and(owner, _BITMASK_ADDRESS)
              // Mask `msgSender` to the lower 160 bits, in case the upper bits somehow aren't clean.
              msgSender := and(msgSender, _BITMASK_ADDRESS)
              // `msgSender == owner || msgSender == approvedAddress`.
              result := or(eq(msgSender, owner), eq(msgSender, approvedAddress))
          }
      }
  
      /**
       * @dev Returns the storage slot and value for the approved address of `tokenId`.
       */
      function _getApprovedSlotAndAddress(uint256 tokenId)
          private
          view
          returns (uint256 approvedAddressSlot, address approvedAddress)
      {
          TokenApprovalRef storage tokenApproval = _tokenApprovals[tokenId];
          // The following is equivalent to `approvedAddress = _tokenApprovals[tokenId].value`.
          assembly {
              approvedAddressSlot := tokenApproval.slot
              approvedAddress := sload(approvedAddressSlot)
          }
      }
  
      // =============================================================
      //                      TRANSFER OPERATIONS
      // =============================================================
  
      /**
       * @dev Transfers `tokenId` from `from` to `to`.
       *
       * Requirements:
       *
       * - `from` cannot be the zero address.
       * - `to` cannot be the zero address.
       * - `tokenId` token must be owned by `from`.
       * - If the caller is not `from`, it must be approved to move this token
       * by either {approve} or {setApprovalForAll}.
       *
       * Emits a {Transfer} event.
       */
      function transferFrom(
          address from,
          address to,
          uint256 tokenId
      ) public payable virtual override {
          uint256 prevOwnershipPacked = _packedOwnershipOf(tokenId);
  
          // Mask `from` to the lower 160 bits, in case the upper bits somehow aren't clean.
          from = address(uint160(uint256(uint160(from)) & _BITMASK_ADDRESS));
  
          if (address(uint160(prevOwnershipPacked)) != from) _revert(TransferFromIncorrectOwner.selector);
  
          (uint256 approvedAddressSlot, address approvedAddress) = _getApprovedSlotAndAddress(tokenId);
  
          // The nested ifs save around 20+ gas over a compound boolean condition.
          if (!_isSenderApprovedOrOwner(approvedAddress, from, _msgSenderERC721A()))
              if (!isApprovedForAll(from, _msgSenderERC721A())) _revert(TransferCallerNotOwnerNorApproved.selector);
  
          _beforeTokenTransfers(from, to, tokenId, 1);
  
          // Clear approvals from the previous owner.
          assembly {
              if approvedAddress {
                  // This is equivalent to `delete _tokenApprovals[tokenId]`.
                  sstore(approvedAddressSlot, 0)
              }
          }
  
          // Underflow of the sender's balance is impossible because we check for
          // ownership above and the recipient's balance can't realistically overflow.
          // Counter overflow is incredibly unrealistic as `tokenId` would have to be 2**256.
          unchecked {
              // We can directly increment and decrement the balances.
              --_packedAddressData[from]; // Updates: `balance -= 1`.
              ++_packedAddressData[to]; // Updates: `balance += 1`.
  
              // Updates:
              // - `address` to the next owner.
              // - `startTimestamp` to the timestamp of transfering.
              // - `burned` to `false`.
              // - `nextInitialized` to `true`.
              _packedOwnerships[tokenId] = _packOwnershipData(
                  to,
                  _BITMASK_NEXT_INITIALIZED | _nextExtraData(from, to, prevOwnershipPacked)
              );
  
              // If the next slot may not have been initialized (i.e. `nextInitialized == false`) .
              if (prevOwnershipPacked & _BITMASK_NEXT_INITIALIZED == 0) {
                  uint256 nextTokenId = tokenId + 1;
                  // If the next slot's address is zero and not burned (i.e. packed value is zero).
                  if (_packedOwnerships[nextTokenId] == 0) {
                      // If the next slot is within bounds.
                      if (nextTokenId != _currentIndex) {
                          // Initialize the next slot to maintain correctness for `ownerOf(tokenId + 1)`.
                          _packedOwnerships[nextTokenId] = prevOwnershipPacked;
                      }
                  }
              }
          }
  
          // Mask `to` to the lower 160 bits, in case the upper bits somehow aren't clean.
          uint256 toMasked = uint256(uint160(to)) & _BITMASK_ADDRESS;
          assembly {
              // Emit the `Transfer` event.
              log4(
                  0, // Start of data (0, since no data).
                  0, // End of data (0, since no data).
                  _TRANSFER_EVENT_SIGNATURE, // Signature.
                  from, // `from`.
                  toMasked, // `to`.
                  tokenId // `tokenId`.
              )
          }
          if (toMasked == 0) _revert(TransferToZeroAddress.selector);
  
          _afterTokenTransfers(from, to, tokenId, 1);
      }
  
      /**
       * @dev Equivalent to `safeTransferFrom(from, to, tokenId, '')`.
       */
      function safeTransferFrom(
          address from,
          address to,
          uint256 tokenId
      ) public payable virtual override {
          safeTransferFrom(from, to, tokenId, '');
      }
  
      /**
       * @dev Safely transfers `tokenId` token from `from` to `to`.
       *
       * Requirements:
       *
       * - `from` cannot be the zero address.
       * - `to` cannot be the zero address.
       * - `tokenId` token must exist and be owned by `from`.
       * - If the caller is not `from`, it must be approved to move this token
       * by either {approve} or {setApprovalForAll}.
       * - If `to` refers to a smart contract, it must implement
       * {IERC721Receiver-onERC721Received}, which is called upon a safe transfer.
       *
       * Emits a {Transfer} event.
       */
      function safeTransferFrom(
          address from,
          address to,
          uint256 tokenId,
          bytes memory _data
      ) public payable virtual override {
          transferFrom(from, to, tokenId);
          if (to.code.length != 0)
              if (!_checkContractOnERC721Received(from, to, tokenId, _data)) {
                  _revert(TransferToNonERC721ReceiverImplementer.selector);
              }
      }
  
      /**
       * @dev Hook that is called before a set of serially-ordered token IDs
       * are about to be transferred. This includes minting.
       * And also called before burning one token.
       *
       * `startTokenId` - the first token ID to be transferred.
       * `quantity` - the amount to be transferred.
       *
       * Calling conditions:
       *
       * - When `from` and `to` are both non-zero, `from`'s `tokenId` will be
       * transferred to `to`.
       * - When `from` is zero, `tokenId` will be minted for `to`.
       * - When `to` is zero, `tokenId` will be burned by `from`.
       * - `from` and `to` are never both zero.
       */
      function _beforeTokenTransfers(
          address from,
          address to,
          uint256 startTokenId,
          uint256 quantity
      ) internal virtual {}
  
      /**
       * @dev Hook that is called after a set of serially-ordered token IDs
       * have been transferred. This includes minting.
       * And also called after one token has been burned.
       *
       * `startTokenId` - the first token ID to be transferred.
       * `quantity` - the amount to be transferred.
       *
       * Calling conditions:
       *
       * - When `from` and `to` are both non-zero, `from`'s `tokenId` has been
       * transferred to `to`.
       * - When `from` is zero, `tokenId` has been minted for `to`.
       * - When `to` is zero, `tokenId` has been burned by `from`.
       * - `from` and `to` are never both zero.
       */
      function _afterTokenTransfers(
          address from,
          address to,
          uint256 startTokenId,
          uint256 quantity
      ) internal virtual {}
  
      /**
       * @dev Private function to invoke {IERC721Receiver-onERC721Received} on a target contract.
       *
       * `from` - Previous owner of the given token ID.
       * `to` - Target address that will receive the token.
       * `tokenId` - Token ID to be transferred.
       * `_data` - Optional data to send along with the call.
       *
       * Returns whether the call correctly returned the expected magic value.
       */
      function _checkContractOnERC721Received(
          address from,
          address to,
          uint256 tokenId,
          bytes memory _data
      ) private returns (bool) {
          try ERC721A__IERC721Receiver(to).onERC721Received(_msgSenderERC721A(), from, tokenId, _data) returns (
              bytes4 retval
          ) {
              return retval == ERC721A__IERC721Receiver(to).onERC721Received.selector;
          } catch (bytes memory reason) {
              if (reason.length == 0) {
                  _revert(TransferToNonERC721ReceiverImplementer.selector);
              }
              assembly {
                  revert(add(32, reason), mload(reason))
              }
          }
      }
  
      // =============================================================
      //                        MINT OPERATIONS
      // =============================================================
  
      /**
       * @dev Mints `quantity` tokens and transfers them to `to`.
       *
       * Requirements:
       *
       * - `to` cannot be the zero address.
       * - `quantity` must be greater than 0.
       *
       * Emits a {Transfer} event for each mint.
       */
      function _mint(address to, uint256 quantity) internal virtual {
          uint256 startTokenId = _currentIndex;
          if (quantity == 0) _revert(MintZeroQuantity.selector);
  
          _beforeTokenTransfers(address(0), to, startTokenId, quantity);
  
          // Overflows are incredibly unrealistic.
          // `balance` and `numberMinted` have a maximum limit of 2**64.
          // `tokenId` has a maximum limit of 2**256.
          unchecked {
              // Updates:
              // - `address` to the owner.
              // - `startTimestamp` to the timestamp of minting.
              // - `burned` to `false`.
              // - `nextInitialized` to `quantity == 1`.
              _packedOwnerships[startTokenId] = _packOwnershipData(
                  to,
                  _nextInitializedFlag(quantity) | _nextExtraData(address(0), to, 0)
              );
  
              // Updates:
              // - `balance += quantity`.
              // - `numberMinted += quantity`.
              //
              // We can directly add to the `balance` and `numberMinted`.
              _packedAddressData[to] += quantity * ((1 << _BITPOS_NUMBER_MINTED) | 1);
  
              // Mask `to` to the lower 160 bits, in case the upper bits somehow aren't clean.
              uint256 toMasked = uint256(uint160(to)) & _BITMASK_ADDRESS;
  
              if (toMasked == 0) _revert(MintToZeroAddress.selector);
  
              uint256 end = startTokenId + quantity;
              uint256 tokenId = startTokenId;
  
              if (end - 1 > _sequentialUpTo()) _revert(SequentialMintExceedsLimit.selector);
  
              do {
                  assembly {
                      // Emit the `Transfer` event.
                      log4(
                          0, // Start of data (0, since no data).
                          0, // End of data (0, since no data).
                          _TRANSFER_EVENT_SIGNATURE, // Signature.
                          0, // `address(0)`.
                          toMasked, // `to`.
                          tokenId // `tokenId`.
                      )
                  }
                  // The `!=` check ensures that large values of `quantity`
                  // that overflows uint256 will make the loop run out of gas.
              } while (++tokenId != end);
  
              _currentIndex = end;
          }
          _afterTokenTransfers(address(0), to, startTokenId, quantity);
      }
  
      /**
       * @dev Mints `quantity` tokens and transfers them to `to`.
       *
       * This function is intended for efficient minting only during contract creation.
       *
       * It emits only one {ConsecutiveTransfer} as defined in
       * [ERC2309](https://eips.ethereum.org/EIPS/eip-2309),
       * instead of a sequence of {Transfer} event(s).
       *
       * Calling this function outside of contract creation WILL make your contract
       * non-compliant with the ERC721 standard.
       * For full ERC721 compliance, substituting ERC721 {Transfer} event(s) with the ERC2309
       * {ConsecutiveTransfer} event is only permissible during contract creation.
       *
       * Requirements:
       *
       * - `to` cannot be the zero address.
       * - `quantity` must be greater than 0.
       *
       * Emits a {ConsecutiveTransfer} event.
       */
      function _mintERC2309(address to, uint256 quantity) internal virtual {
          uint256 startTokenId = _currentIndex;
          if (to == address(0)) _revert(MintToZeroAddress.selector);
          if (quantity == 0) _revert(MintZeroQuantity.selector);
          if (quantity > _MAX_MINT_ERC2309_QUANTITY_LIMIT) _revert(MintERC2309QuantityExceedsLimit.selector);
  
          _beforeTokenTransfers(address(0), to, startTokenId, quantity);
  
          // Overflows are unrealistic due to the above check for `quantity` to be below the limit.
          unchecked {
              // Updates:
              // - `balance += quantity`.
              // - `numberMinted += quantity`.
              //
              // We can directly add to the `balance` and `numberMinted`.
              _packedAddressData[to] += quantity * ((1 << _BITPOS_NUMBER_MINTED) | 1);
  
              // Updates:
              // - `address` to the owner.
              // - `startTimestamp` to the timestamp of minting.
              // - `burned` to `false`.
              // - `nextInitialized` to `quantity == 1`.
              _packedOwnerships[startTokenId] = _packOwnershipData(
                  to,
                  _nextInitializedFlag(quantity) | _nextExtraData(address(0), to, 0)
              );
  
              if (startTokenId + quantity - 1 > _sequentialUpTo()) _revert(SequentialMintExceedsLimit.selector);
  
              emit ConsecutiveTransfer(startTokenId, startTokenId + quantity - 1, address(0), to);
  
              _currentIndex = startTokenId + quantity;
          }
          _afterTokenTransfers(address(0), to, startTokenId, quantity);
      }
  
      /**
       * @dev Safely mints `quantity` tokens and transfers them to `to`.
       *
       * Requirements:
       *
       * - If `to` refers to a smart contract, it must implement
       * {IERC721Receiver-onERC721Received}, which is called for each safe transfer.
       * - `quantity` must be greater than 0.
       *
       * See {_mint}.
       *
       * Emits a {Transfer} event for each mint.
       */
      function _safeMint(
          address to,
          uint256 quantity,
          bytes memory _data
      ) internal virtual {
          _mint(to, quantity);
  
          unchecked {
              if (to.code.length != 0) {
                  uint256 end = _currentIndex;
                  uint256 index = end - quantity;
                  do {
                      if (!_checkContractOnERC721Received(address(0), to, index++, _data)) {
                          _revert(TransferToNonERC721ReceiverImplementer.selector);
                      }
                  } while (index < end);
                  // This prevents reentrancy to `_safeMint`.
                  // It does not prevent reentrancy to `_safeMintSpot`.
                  if (_currentIndex != end) revert();
              }
          }
      }
  
      /**
       * @dev Equivalent to `_safeMint(to, quantity, '')`.
       */
      function _safeMint(address to, uint256 quantity) internal virtual {
          _safeMint(to, quantity, '');
      }
  
      /**
       * @dev Mints a single token at `tokenId`.
       *
       * Note: A spot-minted `tokenId` that has been burned can be re-minted again.
       *
       * Requirements:
       *
       * - `to` cannot be the zero address.
       * - `tokenId` must be greater than `_sequentialUpTo()`.
       * - `tokenId` must not exist.
       *
       * Emits a {Transfer} event for each mint.
       */
      function _mintSpot(address to, uint256 tokenId) internal virtual {
          if (tokenId <= _sequentialUpTo()) _revert(SpotMintTokenIdTooSmall.selector);
          uint256 prevOwnershipPacked = _packedOwnerships[tokenId];
          if (_packedOwnershipExists(prevOwnershipPacked)) _revert(TokenAlreadyExists.selector);
  
          _beforeTokenTransfers(address(0), to, tokenId, 1);
  
          // Overflows are incredibly unrealistic.
          // The `numberMinted` for `to` is incremented by 1, and has a max limit of 2**64 - 1.
          // `_spotMinted` is incremented by 1, and has a max limit of 2**256 - 1.
          unchecked {
              // Updates:
              // - `address` to the owner.
              // - `startTimestamp` to the timestamp of minting.
              // - `burned` to `false`.
              // - `nextInitialized` to `true` (as `quantity == 1`).
              _packedOwnerships[tokenId] = _packOwnershipData(
                  to,
                  _nextInitializedFlag(1) | _nextExtraData(address(0), to, prevOwnershipPacked)
              );
  
              // Updates:
              // - `balance += 1`.
              // - `numberMinted += 1`.
              //
              // We can directly add to the `balance` and `numberMinted`.
              _packedAddressData[to] += (1 << _BITPOS_NUMBER_MINTED) | 1;
  
              // Mask `to` to the lower 160 bits, in case the upper bits somehow aren't clean.
              uint256 toMasked = uint256(uint160(to)) & _BITMASK_ADDRESS;
  
              if (toMasked == 0) _revert(MintToZeroAddress.selector);
  
              assembly {
                  // Emit the `Transfer` event.
                  log4(
                      0, // Start of data (0, since no data).
                      0, // End of data (0, since no data).
                      _TRANSFER_EVENT_SIGNATURE, // Signature.
                      0, // `address(0)`.
                      toMasked, // `to`.
                      tokenId // `tokenId`.
                  )
              }
  
              ++_spotMinted;
          }
  
          _afterTokenTransfers(address(0), to, tokenId, 1);
      }
  
      /**
       * @dev Safely mints a single token at `tokenId`.
       *
       * Note: A spot-minted `tokenId` that has been burned can be re-minted again.
       *
       * Requirements:
       *
       * - If `to` refers to a smart contract, it must implement {IERC721Receiver-onERC721Received}.
       * - `tokenId` must be greater than `_sequentialUpTo()`.
       * - `tokenId` must not exist.
       *
       * See {_mintSpot}.
       *
       * Emits a {Transfer} event.
       */
      function _safeMintSpot(
          address to,
          uint256 tokenId,
          bytes memory _data
      ) internal virtual {
          _mintSpot(to, tokenId);
  
          unchecked {
              if (to.code.length != 0) {
                  uint256 currentSpotMinted = _spotMinted;
                  if (!_checkContractOnERC721Received(address(0), to, tokenId, _data)) {
                      _revert(TransferToNonERC721ReceiverImplementer.selector);
                  }
                  // This prevents reentrancy to `_safeMintSpot`.
                  // It does not prevent reentrancy to `_safeMint`.
                  if (_spotMinted != currentSpotMinted) revert();
              }
          }
      }
  
      /**
       * @dev Equivalent to `_safeMintSpot(to, tokenId, '')`.
       */
      function _safeMintSpot(address to, uint256 tokenId) internal virtual {
          _safeMintSpot(to, tokenId, '');
      }
  
      // =============================================================
      //                       APPROVAL OPERATIONS
      // =============================================================
  
      /**
       * @dev Equivalent to `_approve(to, tokenId, false)`.
       */
      function _approve(address to, uint256 tokenId) internal virtual {
          _approve(to, tokenId, false);
      }
  
      /**
       * @dev Gives permission to `to` to transfer `tokenId` token to another account.
       * The approval is cleared when the token is transferred.
       *
       * Only a single account can be approved at a time, so approving the
       * zero address clears previous approvals.
       *
       * Requirements:
       *
       * - `tokenId` must exist.
       *
       * Emits an {Approval} event.
       */
      function _approve(
          address to,
          uint256 tokenId,
          bool approvalCheck
      ) internal virtual {
          address owner = ownerOf(tokenId);
  
          if (approvalCheck && _msgSenderERC721A() != owner)
              if (!isApprovedForAll(owner, _msgSenderERC721A())) {
                  _revert(ApprovalCallerNotOwnerNorApproved.selector);
              }
  
          _tokenApprovals[tokenId].value = to;
          emit Approval(owner, to, tokenId);
      }
  
      // =============================================================
      //                        BURN OPERATIONS
      // =============================================================
  
      /**
       * @dev Equivalent to `_burn(tokenId, false)`.
       */
      function _burn(uint256 tokenId) internal virtual {
          _burn(tokenId, false);
      }
  
      /**
       * @dev Destroys `tokenId`.
       * The approval is cleared when the token is burned.
       *
       * Requirements:
       *
       * - `tokenId` must exist.
       *
       * Emits a {Transfer} event.
       */
      function _burn(uint256 tokenId, bool approvalCheck) internal virtual {
          uint256 prevOwnershipPacked = _packedOwnershipOf(tokenId);
  
          address from = address(uint160(prevOwnershipPacked));
  
          (uint256 approvedAddressSlot, address approvedAddress) = _getApprovedSlotAndAddress(tokenId);
  
          if (approvalCheck) {
              // The nested ifs save around 20+ gas over a compound boolean condition.
              if (!_isSenderApprovedOrOwner(approvedAddress, from, _msgSenderERC721A()))
                  if (!isApprovedForAll(from, _msgSenderERC721A())) _revert(TransferCallerNotOwnerNorApproved.selector);
          }
  
          _beforeTokenTransfers(from, address(0), tokenId, 1);
  
          // Clear approvals from the previous owner.
          assembly {
              if approvedAddress {
                  // This is equivalent to `delete _tokenApprovals[tokenId]`.
                  sstore(approvedAddressSlot, 0)
              }
          }
  
          // Underflow of the sender's balance is impossible because we check for
          // ownership above and the recipient's balance can't realistically overflow.
          // Counter overflow is incredibly unrealistic as `tokenId` would have to be 2**256.
          unchecked {
              // Updates:
              // - `balance -= 1`.
              // - `numberBurned += 1`.
              //
              // We can directly decrement the balance, and increment the number burned.
              // This is equivalent to `packed -= 1; packed += 1 << _BITPOS_NUMBER_BURNED;`.
              _packedAddressData[from] += (1 << _BITPOS_NUMBER_BURNED) - 1;
  
              // Updates:
              // - `address` to the last owner.
              // - `startTimestamp` to the timestamp of burning.
              // - `burned` to `true`.
              // - `nextInitialized` to `true`.
              _packedOwnerships[tokenId] = _packOwnershipData(
                  from,
                  (_BITMASK_BURNED | _BITMASK_NEXT_INITIALIZED) | _nextExtraData(from, address(0), prevOwnershipPacked)
              );
  
              // If the next slot may not have been initialized (i.e. `nextInitialized == false`) .
              if (prevOwnershipPacked & _BITMASK_NEXT_INITIALIZED == 0) {
                  uint256 nextTokenId = tokenId + 1;
                  // If the next slot's address is zero and not burned (i.e. packed value is zero).
                  if (_packedOwnerships[nextTokenId] == 0) {
                      // If the next slot is within bounds.
                      if (nextTokenId != _currentIndex) {
                          // Initialize the next slot to maintain correctness for `ownerOf(tokenId + 1)`.
                          _packedOwnerships[nextTokenId] = prevOwnershipPacked;
                      }
                  }
              }
          }
  
          emit Transfer(from, address(0), tokenId);
          _afterTokenTransfers(from, address(0), tokenId, 1);
  
          // Overflow not possible, as `_burnCounter` cannot be exceed `_currentIndex + _spotMinted` times.
          unchecked {
              _burnCounter++;
          }
      }
  
      // =============================================================
      //                     EXTRA DATA OPERATIONS
      // =============================================================
  
      /**
       * @dev Directly sets the extra data for the ownership data `index`.
       */
      function _setExtraDataAt(uint256 index, uint24 extraData) internal virtual {
          uint256 packed = _packedOwnerships[index];
          if (packed == 0) _revert(OwnershipNotInitializedForExtraData.selector);
          uint256 extraDataCasted;
          // Cast `extraData` with assembly to avoid redundant masking.
          assembly {
              extraDataCasted := extraData
          }
          packed = (packed & _BITMASK_EXTRA_DATA_COMPLEMENT) | (extraDataCasted << _BITPOS_EXTRA_DATA);
          _packedOwnerships[index] = packed;
      }
  
      /**
       * @dev Called during each token transfer to set the 24bit `extraData` field.
       * Intended to be overridden by the cosumer contract.
       *
       * `previousExtraData` - the value of `extraData` before transfer.
       *
       * Calling conditions:
       *
       * - When `from` and `to` are both non-zero, `from`'s `tokenId` will be
       * transferred to `to`.
       * - When `from` is zero, `tokenId` will be minted for `to`.
       * - When `to` is zero, `tokenId` will be burned by `from`.
       * - `from` and `to` are never both zero.
       */
      function _extraData(
          address from,
          address to,
          uint24 previousExtraData
      ) internal view virtual returns (uint24) {}
  
      /**
       * @dev Returns the next extra data for the packed ownership data.
       * The returned result is shifted into position.
       */
      function _nextExtraData(
          address from,
          address to,
          uint256 prevOwnershipPacked
      ) private view returns (uint256) {
          uint24 extraData = uint24(prevOwnershipPacked >> _BITPOS_EXTRA_DATA);
          return uint256(_extraData(from, to, extraData)) << _BITPOS_EXTRA_DATA;
      }
  
      // =============================================================
      //                       OTHER OPERATIONS
      // =============================================================
  
      /**
       * @dev Returns the message sender (defaults to `msg.sender`).
       *
       * If you are writing GSN compatible contracts, you need to override this function.
       */
      function _msgSenderERC721A() internal view virtual returns (address) {
          return msg.sender;
      }
  
      /**
       * @dev Converts a uint256 to its ASCII string decimal representation.
       */
      function _toString(uint256 value) internal pure virtual returns (string memory str) {
          assembly {
              // The maximum value of a uint256 contains 78 digits (1 byte per digit), but
              // we allocate 0xa0 bytes to keep the free memory pointer 32-byte word aligned.
              // We will need 1 word for the trailing zeros padding, 1 word for the length,
              // and 3 words for a maximum of 78 digits. Total: 5 * 0x20 = 0xa0.
              let m := add(mload(0x40), 0xa0)
              // Update the free memory pointer to allocate.
              mstore(0x40, m)
              // Assign the `str` to the end.
              str := sub(m, 0x20)
              // Zeroize the slot after the string.
              mstore(str, 0)
  
              // Cache the end of the memory to calculate the length later.
              let end := str
  
              // We write the string from rightmost digit to leftmost digit.
              // The following is essentially a do-while loop that also handles the zero case.
              // prettier-ignore
              for { let temp := value } 1 {} {
                  str := sub(str, 1)
                  // Write the character to the pointer.
                  // The ASCII index of the '0' character is 48.
                  mstore8(str, add(48, mod(temp, 10)))
                  // Keep dividing `temp` until zero.
                  temp := div(temp, 10)
                  // prettier-ignore
                  if iszero(temp) { break }
              }
  
              let length := sub(end, str)
              // Move the pointer 32 bytes leftwards to make room for the length.
              str := sub(str, 0x20)
              // Store the length.
              mstore(str, length)
          }
      }
  
      /**
       * @dev For more efficient reverts.
       */
      function _revert(bytes4 errorSelector) internal pure {
          assembly {
              mstore(0x00, errorSelector)
              revert(0x00, 0x04)
          }
      }
  }
  
  // File: contracts/Onionz_.sol
  
  
  pragma solidity ^0.8.9;
  
  
  
  
  
  contract Onionz is Ownable, ERC721A, ReentrancyGuard {
      uint256 public constant MAX_FREE_MINT = 20;
  
      uint256 public maxSupply = 1000;
  
      bool public freeSaleOn;
  
      mapping(address => uint256) public whiteList;
  
      // metadata URI
      string private _baseTokenURI;
  
      constructor(address initialOwner)
          ERC721A("Onionz", "ONNZ")
          Ownable(initialOwner)
      {
          _baseTokenURI = "ipfs://QmXi6VXkky1TeStrsTuJ6jTqSDFZZuqPxPfNDrsgTUKC3u/";
      }
  
      modifier callerIsUser() {
          require(tx.origin == msg.sender, "The caller is another contract");
          _;
      }
  
      // free
      function freeMint(uint256 amount) external payable callerIsUser {
          require(freeSaleOn, "free mint has not begun yet");
          require(
              whiteList[msg.sender] > 0,
              "you are not eligible for whiteList"
          );
          require(amount <= whiteList[msg.sender], "not eligible for whiteList");
          require(amount > 0, "mint must more than 0 token");
          require(totalSupply() + amount <= maxSupply, "reached max supply");
          whiteList[msg.sender] -= amount;
          _safeMint(msg.sender, amount);
      }
  
      function setFreeSale(bool _on, address[] memory addresses)
          external
          onlyOwner
      {
          freeSaleOn = _on;
          for (uint256 i = 0; i < addresses.length; i++) {
              whiteList[addresses[i]] = MAX_FREE_MINT;
          }
      }
  
      function _startTokenId() internal view virtual override returns (uint256) {
          return 1;
      }
  
      function _baseURI() internal view virtual override returns (string memory) {
          return _baseTokenURI;
      }
  
      function tokenURI(uint256 tokenId)
          public
          view
          virtual
          override
          returns (string memory)
      {
          if (!_exists(tokenId)) revert URIQueryForNonexistentToken();
  
          string memory baseURI = _baseURI();
          return
              bytes(baseURI).length != 0
                  ? string(
                      abi.encodePacked(baseURI, Strings.toString(tokenId - 1))
                  )
                  : "";
      }
  
      function setBaseURI(string calldata baseURI) external onlyOwner {
          _baseTokenURI = baseURI;
      }
  
      function withdraw() external onlyOwner nonReentrant {
          (bool success, ) = msg.sender.call{value: address(this).balance}("");
          require(success, "Transfer failed");
      }
  }