creation_sourcecode: // File: @openzeppelin/contracts/token/ERC20/IERC20.sol
  // OpenZeppelin Contracts (last updated v4.6.0) (token/ERC20/IERC20.sol)
  // SPDX-License-Identifier: MIT
  pragma solidity ^0.8.0;
  
  /**
   * @dev Interface of the ERC20 standard as defined in the EIP.
   */
  interface IERC20 {
      /**
       * @dev Emitted when `value` tokens are moved from one account (`from`) to
       * another (`to`).
       *
       * Note that `value` may be zero.
       */
      event Transfer(address indexed from, address indexed to, uint256 value);
  
      /**
       * @dev Emitted when the allowance of a `spender` for an `owner` is set by
       * a call to {approve}. `value` is the new allowance.
       */
      event Approval(address indexed owner, address indexed spender, uint256 value);
  
      /**
       * @dev Returns the amount of tokens in existence.
       */
      function totalSupply() external view returns (uint256);
  
      /**
       * @dev Returns the amount of tokens owned by `account`.
       */
      function balanceOf(address account) external view returns (uint256);
  
      /**
       * @dev Moves `amount` tokens from the caller's account to `to`.
       *
       * Returns a boolean value indicating whether the operation succeeded.
       *
       * Emits a {Transfer} event.
       */
      function transfer(address to, uint256 amount) external returns (bool);
  
      /**
       * @dev Returns the remaining number of tokens that `spender` will be
       * allowed to spend on behalf of `owner` through {transferFrom}. This is
       * zero by default.
       *
       * This value changes when {approve} or {transferFrom} are called.
       */
      function allowance(address owner, address spender) external view returns (uint256);
  
      /**
       * @dev Sets `amount` as the allowance of `spender` over the caller's tokens.
       *
       * Returns a boolean value indicating whether the operation succeeded.
       *
       * IMPORTANT: Beware that changing an allowance with this method brings the risk
       * that someone may use both the old and the new allowance by unfortunate
       * transaction ordering. One possible solution to mitigate this race
       * condition is to first reduce the spender's allowance to 0 and set the
       * desired value afterwards:
       * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
       *
       * Emits an {Approval} event.
       */
      function approve(address spender, uint256 amount) external returns (bool);
  
      /**
       * @dev Moves `amount` tokens from `from` to `to` using the
       * allowance mechanism. `amount` is then deducted from the caller's
       * allowance.
       *
       * Returns a boolean value indicating whether the operation succeeded.
       *
       * Emits a {Transfer} event.
       */
      function transferFrom(
          address from,
          address to,
          uint256 amount
      ) external returns (bool);
  }
  
  // File: @openzeppelin/contracts/token/ERC20/extensions/IERC20Metadata.sol
  
  
  // OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/IERC20Metadata.sol)
  
  pragma solidity ^0.8.0;
  
  /**
   * @dev Interface for the optional metadata functions from the ERC20 standard.
   *
   * _Available since v4.1._
   */
  interface IERC20Metadata is IERC20 {
      /**
       * @dev Returns the name of the token.
       */
      function name() external view returns (string memory);
  
      /**
       * @dev Returns the symbol of the token.
       */
      function symbol() external view returns (string memory);
  
      /**
       * @dev Returns the decimals places of the token.
       */
      function decimals() external view returns (uint8);
  }
  
  // File: @openzeppelin/contracts/utils/Context.sol
  
  
  // OpenZeppelin Contracts v4.4.1 (utils/Context.sol)
  
  pragma solidity ^0.8.0;
  
  /**
   * @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;
      }
  }
  
  // File: @openzeppelin/contracts/token/ERC20/ERC20.sol
  
  
  // OpenZeppelin Contracts (last updated v4.8.0) (token/ERC20/ERC20.sol)
  
  pragma solidity ^0.8.0;
  
  
  
  /**
   * @dev Implementation of the {IERC20} interface.
   *
   * This implementation is agnostic to the way tokens are created. This means
   * that a supply mechanism has to be added in a derived contract using {_mint}.
   * For a generic mechanism see {ERC20PresetMinterPauser}.
   *
   * TIP: For a detailed writeup see our guide
   * https://forum.openzeppelin.com/t/how-to-implement-erc20-supply-mechanisms/226[How
   * to implement supply mechanisms].
   *
   * We have followed general OpenZeppelin Contracts guidelines: functions revert
   * instead returning `false` on failure. This behavior is nonetheless
   * conventional and does not conflict with the expectations of ERC20
   * applications.
   *
   * Additionally, an {Approval} event is emitted on calls to {transferFrom}.
   * This allows applications to reconstruct the allowance for all accounts just
   * by listening to said events. Other implementations of the EIP may not emit
   * these events, as it isn't required by the specification.
   *
   * Finally, the non-standard {decreaseAllowance} and {increaseAllowance}
   * functions have been added to mitigate the well-known issues around setting
   * allowances. See {IERC20-approve}.
   */
  contract ERC20 is Context, IERC20, IERC20Metadata {
      mapping(address => uint256) private _balances;
  
      mapping(address => mapping(address => uint256)) private _allowances;
  
      uint256 private _totalSupply;
  
      string private _name;
      string private _symbol;
  
      /**
       * @dev Sets the values for {name} and {symbol}.
       *
       * The default value of {decimals} is 18. To select a different value for
       * {decimals} you should overload it.
       *
       * All two of these values are immutable: they can only be set once during
       * construction.
       */
      constructor(string memory name_, string memory symbol_) {
          _name = name_;
          _symbol = symbol_;
      }
  
      /**
       * @dev Returns the name of the token.
       */
      function name() public view virtual override returns (string memory) {
          return _name;
      }
  
      /**
       * @dev Returns the symbol of the token, usually a shorter version of the
       * name.
       */
      function symbol() public view virtual override returns (string memory) {
          return _symbol;
      }
  
      /**
       * @dev Returns the number of decimals used to get its user representation.
       * For example, if `decimals` equals `2`, a balance of `505` tokens should
       * be displayed to a user as `5.05` (`505 / 10 ** 2`).
       *
       * Tokens usually opt for a value of 18, imitating the relationship between
       * Ether and Wei. This is the value {ERC20} uses, unless this function is
       * overridden;
       *
       * NOTE: This information is only used for _display_ purposes: it in
       * no way affects any of the arithmetic of the contract, including
       * {IERC20-balanceOf} and {IERC20-transfer}.
       */
      function decimals() public view virtual override returns (uint8) {
          return 18;
      }
  
      /**
       * @dev See {IERC20-totalSupply}.
       */
      function totalSupply() public view virtual override returns (uint256) {
          return _totalSupply;
      }
  
      /**
       * @dev See {IERC20-balanceOf}.
       */
      function balanceOf(address account) public view virtual override returns (uint256) {
          return _balances[account];
      }
  
      /**
       * @dev See {IERC20-transfer}.
       *
       * Requirements:
       *
       * - `to` cannot be the zero address.
       * - the caller must have a balance of at least `amount`.
       */
      function transfer(address to, uint256 amount) public virtual override returns (bool) {
          address owner = _msgSender();
          _transfer(owner, to, amount);
          return true;
      }
  
      /**
       * @dev See {IERC20-allowance}.
       */
      function allowance(address owner, address spender) public view virtual override returns (uint256) {
          return _allowances[owner][spender];
      }
  
      /**
       * @dev See {IERC20-approve}.
       *
       * NOTE: If `amount` is the maximum `uint256`, the allowance is not updated on
       * `transferFrom`. This is semantically equivalent to an infinite approval.
       *
       * Requirements:
       *
       * - `spender` cannot be the zero address.
       */
      function approve(address spender, uint256 amount) public virtual override returns (bool) {
          address owner = _msgSender();
          _approve(owner, spender, amount);
          return true;
      }
  
      /**
       * @dev See {IERC20-transferFrom}.
       *
       * Emits an {Approval} event indicating the updated allowance. This is not
       * required by the EIP. See the note at the beginning of {ERC20}.
       *
       * NOTE: Does not update the allowance if the current allowance
       * is the maximum `uint256`.
       *
       * Requirements:
       *
       * - `from` and `to` cannot be the zero address.
       * - `from` must have a balance of at least `amount`.
       * - the caller must have allowance for ``from``'s tokens of at least
       * `amount`.
       */
      function transferFrom(
          address from,
          address to,
          uint256 amount
      ) public virtual override returns (bool) {
          address spender = _msgSender();
          _spendAllowance(from, spender, amount);
          _transfer(from, to, amount);
          return true;
      }
  
      /**
       * @dev Atomically increases the allowance granted to `spender` by the caller.
       *
       * This is an alternative to {approve} that can be used as a mitigation for
       * problems described in {IERC20-approve}.
       *
       * Emits an {Approval} event indicating the updated allowance.
       *
       * Requirements:
       *
       * - `spender` cannot be the zero address.
       */
      function increaseAllowance(address spender, uint256 addedValue) public virtual returns (bool) {
          address owner = _msgSender();
          _approve(owner, spender, allowance(owner, spender) + addedValue);
          return true;
      }
  
      /**
       * @dev Atomically decreases the allowance granted to `spender` by the caller.
       *
       * This is an alternative to {approve} that can be used as a mitigation for
       * problems described in {IERC20-approve}.
       *
       * Emits an {Approval} event indicating the updated allowance.
       *
       * Requirements:
       *
       * - `spender` cannot be the zero address.
       * - `spender` must have allowance for the caller of at least
       * `subtractedValue`.
       */
      function decreaseAllowance(address spender, uint256 subtractedValue) public virtual returns (bool) {
          address owner = _msgSender();
          uint256 currentAllowance = allowance(owner, spender);
          require(currentAllowance >= subtractedValue, "ERC20: decreased allowance below zero");
          unchecked {
              _approve(owner, spender, currentAllowance - subtractedValue);
          }
  
          return true;
      }
  
      /**
       * @dev Moves `amount` of tokens from `from` to `to`.
       *
       * This internal function is equivalent to {transfer}, and can be used to
       * e.g. implement automatic token fees, slashing mechanisms, etc.
       *
       * Emits a {Transfer} event.
       *
       * Requirements:
       *
       * - `from` cannot be the zero address.
       * - `to` cannot be the zero address.
       * - `from` must have a balance of at least `amount`.
       */
      function _transfer(
          address from,
          address to,
          uint256 amount
      ) internal virtual {
          require(from != address(0), "ERC20: transfer from the zero address");
          require(to != address(0), "ERC20: transfer to the zero address");
  
          _beforeTokenTransfer(from, to, amount);
  
          uint256 fromBalance = _balances[from];
          require(fromBalance >= amount, "ERC20: transfer amount exceeds balance");
          unchecked {
              _balances[from] = fromBalance - amount;
              // Overflow not possible: the sum of all balances is capped by totalSupply, and the sum is preserved by
              // decrementing then incrementing.
              _balances[to] += amount;
          }
  
          emit Transfer(from, to, amount);
  
          _afterTokenTransfer(from, to, amount);
      }
  
      /** @dev Creates `amount` tokens and assigns them to `account`, increasing
       * the total supply.
       *
       * Emits a {Transfer} event with `from` set to the zero address.
       *
       * Requirements:
       *
       * - `account` cannot be the zero address.
       */
      function _mint(address account, uint256 amount) internal virtual {
          require(account != address(0), "ERC20: mint to the zero address");
  
          _beforeTokenTransfer(address(0), account, amount);
  
          _totalSupply += amount;
          unchecked {
              // Overflow not possible: balance + amount is at most totalSupply + amount, which is checked above.
              _balances[account] += amount;
          }
          emit Transfer(address(0), account, amount);
  
          _afterTokenTransfer(address(0), account, amount);
      }
  
      /**
       * @dev Destroys `amount` tokens from `account`, reducing the
       * total supply.
       *
       * Emits a {Transfer} event with `to` set to the zero address.
       *
       * Requirements:
       *
       * - `account` cannot be the zero address.
       * - `account` must have at least `amount` tokens.
       */
      function _burn(address account, uint256 amount) internal virtual {
          require(account != address(0), "ERC20: burn from the zero address");
  
          _beforeTokenTransfer(account, address(0), amount);
  
          uint256 accountBalance = _balances[account];
          require(accountBalance >= amount, "ERC20: burn amount exceeds balance");
          unchecked {
              _balances[account] = accountBalance - amount;
              // Overflow not possible: amount <= accountBalance <= totalSupply.
              _totalSupply -= amount;
          }
  
          emit Transfer(account, address(0), amount);
  
          _afterTokenTransfer(account, address(0), amount);
      }
  
      /**
       * @dev Sets `amount` as the allowance of `spender` over the `owner` s tokens.
       *
       * This internal function is equivalent to `approve`, and can be used to
       * e.g. set automatic allowances for certain subsystems, etc.
       *
       * Emits an {Approval} event.
       *
       * Requirements:
       *
       * - `owner` cannot be the zero address.
       * - `spender` cannot be the zero address.
       */
      function _approve(
          address owner,
          address spender,
          uint256 amount
      ) internal virtual {
          require(owner != address(0), "ERC20: approve from the zero address");
          require(spender != address(0), "ERC20: approve to the zero address");
  
          _allowances[owner][spender] = amount;
          emit Approval(owner, spender, amount);
      }
  
      /**
       * @dev Updates `owner` s allowance for `spender` based on spent `amount`.
       *
       * Does not update the allowance amount in case of infinite allowance.
       * Revert if not enough allowance is available.
       *
       * Might emit an {Approval} event.
       */
      function _spendAllowance(
          address owner,
          address spender,
          uint256 amount
      ) internal virtual {
          uint256 currentAllowance = allowance(owner, spender);
          if (currentAllowance != type(uint256).max) {
              require(currentAllowance >= amount, "ERC20: insufficient allowance");
              unchecked {
                  _approve(owner, spender, currentAllowance - amount);
              }
          }
      }
  
      /**
       * @dev Hook that is called before any transfer of tokens. This includes
       * minting and burning.
       *
       * Calling conditions:
       *
       * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
       * will be transferred to `to`.
       * - when `from` is zero, `amount` tokens will be minted for `to`.
       * - when `to` is zero, `amount` of ``from``'s tokens will be burned.
       * - `from` and `to` are never both zero.
       *
       * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
       */
      function _beforeTokenTransfer(
          address from,
          address to,
          uint256 amount
      ) internal virtual {}
  
      /**
       * @dev Hook that is called after any transfer of tokens. This includes
       * minting and burning.
       *
       * Calling conditions:
       *
       * - when `from` and `to` are both non-zero, `amount` of ``from``'s tokens
       * has been transferred to `to`.
       * - when `from` is zero, `amount` tokens have been minted for `to`.
       * - when `to` is zero, `amount` of ``from``'s tokens have been burned.
       * - `from` and `to` are never both zero.
       *
       * To learn more about hooks, head to xref:ROOT:extending-contracts.adoc#using-hooks[Using Hooks].
       */
      function _afterTokenTransfer(
          address from,
          address to,
          uint256 amount
      ) internal virtual {}
  }
  
  // File: @openzeppelin/contracts/token/ERC20/extensions/ERC20Burnable.sol
  
  
  // OpenZeppelin Contracts (last updated v4.5.0) (token/ERC20/extensions/ERC20Burnable.sol)
  
  pragma solidity ^0.8.0;
  
  
  /**
   * @dev Extension of {ERC20} that allows token holders to destroy both their own
   * tokens and those that they have an allowance for, in a way that can be
   * recognized off-chain (via event analysis).
   */
  abstract contract ERC20Burnable is Context, ERC20 {
      /**
       * @dev Destroys `amount` tokens from the caller.
       *
       * See {ERC20-_burn}.
       */
      function burn(uint256 amount) public virtual {
          _burn(_msgSender(), amount);
      }
  
      /**
       * @dev Destroys `amount` tokens from `account`, deducting from the caller's
       * allowance.
       *
       * See {ERC20-_burn} and {ERC20-allowance}.
       *
       * Requirements:
       *
       * - the caller must have allowance for ``accounts``'s tokens of at least
       * `amount`.
       */
      function burnFrom(address account, uint256 amount) public virtual {
          _spendAllowance(account, _msgSender(), amount);
          _burn(account, amount);
      }
  }
  
  // File: @openzeppelin/contracts/security/Pausable.sol
  
  
  // OpenZeppelin Contracts (last updated v4.7.0) (security/Pausable.sol)
  
  pragma solidity ^0.8.0;
  
  /**
   * @dev Contract module which allows children to implement an emergency stop
   * mechanism that can be triggered by an authorized account.
   *
   * This module is used through inheritance. It will make available the
   * modifiers `whenNotPaused` and `whenPaused`, which can be applied to
   * the functions of your contract. Note that they will not be pausable by
   * simply including this module, only once the modifiers are put in place.
   */
  abstract contract Pausable is Context {
      /**
       * @dev Emitted when the pause is triggered by `account`.
       */
      event Paused(address account);
  
      /**
       * @dev Emitted when the pause is lifted by `account`.
       */
      event Unpaused(address account);
  
      bool private _paused;
  
      /**
       * @dev Initializes the contract in unpaused state.
       */
      constructor() {
          _paused = false;
      }
  
      /**
       * @dev Modifier to make a function callable only when the contract is not paused.
       *
       * Requirements:
       *
       * - The contract must not be paused.
       */
      modifier whenNotPaused() {
          _requireNotPaused();
          _;
      }
  
      /**
       * @dev Modifier to make a function callable only when the contract is paused.
       *
       * Requirements:
       *
       * - The contract must be paused.
       */
      modifier whenPaused() {
          _requirePaused();
          _;
      }
  
      /**
       * @dev Returns true if the contract is paused, and false otherwise.
       */
      function paused() public view virtual returns (bool) {
          return _paused;
      }
  
      /**
       * @dev Throws if the contract is paused.
       */
      function _requireNotPaused() internal view virtual {
          require(!paused(), "Pausable: paused");
      }
  
      /**
       * @dev Throws if the contract is not paused.
       */
      function _requirePaused() internal view virtual {
          require(paused(), "Pausable: not paused");
      }
  
      /**
       * @dev Triggers stopped state.
       *
       * Requirements:
       *
       * - The contract must not be paused.
       */
      function _pause() internal virtual whenNotPaused {
          _paused = true;
          emit Paused(_msgSender());
      }
  
      /**
       * @dev Returns to normal state.
       *
       * Requirements:
       *
       * - The contract must be paused.
       */
      function _unpause() internal virtual whenPaused {
          _paused = false;
          emit Unpaused(_msgSender());
      }
  }
  
  // File: @openzeppelin/contracts/token/ERC20/extensions/ERC20Pausable.sol
  
  
  // OpenZeppelin Contracts v4.4.1 (token/ERC20/extensions/ERC20Pausable.sol)
  
  pragma solidity ^0.8.0;
  
  
  /**
   * @dev ERC20 token with pausable token transfers, minting and burning.
   *
   * Useful for scenarios such as preventing trades until the end of an evaluation
   * period, or having an emergency switch for freezing all token transfers in the
   * event of a large bug.
   */
  abstract contract ERC20Pausable is ERC20, Pausable {
      /**
       * @dev See {ERC20-_beforeTokenTransfer}.
       *
       * Requirements:
       *
       * - the contract must not be paused.
       */
      function _beforeTokenTransfer(
          address from,
          address to,
          uint256 amount
      ) internal virtual override {
          super._beforeTokenTransfer(from, to, amount);
  
          require(!paused(), "ERC20Pausable: token transfer while paused");
      }
  }
  
  // File: @openzeppelin/contracts/access/IAccessControl.sol
  
  
  // OpenZeppelin Contracts v4.4.1 (access/IAccessControl.sol)
  
  pragma solidity ^0.8.0;
  
  /**
   * @dev External interface of AccessControl declared to support ERC165 detection.
   */
  interface IAccessControl {
      /**
       * @dev Emitted when `newAdminRole` is set as ``role``'s admin role, replacing `previousAdminRole`
       *
       * `DEFAULT_ADMIN_ROLE` is the starting admin for all roles, despite
       * {RoleAdminChanged} not being emitted signaling this.
       *
       * _Available since v3.1._
       */
      event RoleAdminChanged(bytes32 indexed role, bytes32 indexed previousAdminRole, bytes32 indexed newAdminRole);
  
      /**
       * @dev Emitted when `account` is granted `role`.
       *
       * `sender` is the account that originated the contract call, an admin role
       * bearer except when using {AccessControl-_setupRole}.
       */
      event RoleGranted(bytes32 indexed role, address indexed account, address indexed sender);
  
      /**
       * @dev Emitted when `account` is revoked `role`.
       *
       * `sender` is the account that originated the contract call:
       *   - if using `revokeRole`, it is the admin role bearer
       *   - if using `renounceRole`, it is the role bearer (i.e. `account`)
       */
      event RoleRevoked(bytes32 indexed role, address indexed account, address indexed sender);
  
      /**
       * @dev Returns `true` if `account` has been granted `role`.
       */
      function hasRole(bytes32 role, address account) external view returns (bool);
  
      /**
       * @dev Returns the admin role that controls `role`. See {grantRole} and
       * {revokeRole}.
       *
       * To change a role's admin, use {AccessControl-_setRoleAdmin}.
       */
      function getRoleAdmin(bytes32 role) external view returns (bytes32);
  
      /**
       * @dev Grants `role` to `account`.
       *
       * If `account` had not been already granted `role`, emits a {RoleGranted}
       * event.
       *
       * Requirements:
       *
       * - the caller must have ``role``'s admin role.
       */
      function grantRole(bytes32 role, address account) external;
  
      /**
       * @dev Revokes `role` from `account`.
       *
       * If `account` had been granted `role`, emits a {RoleRevoked} event.
       *
       * Requirements:
       *
       * - the caller must have ``role``'s admin role.
       */
      function revokeRole(bytes32 role, address account) external;
  
      /**
       * @dev Revokes `role` from the calling account.
       *
       * Roles are often managed via {grantRole} and {revokeRole}: this function's
       * purpose is to provide a mechanism for accounts to lose their privileges
       * if they are compromised (such as when a trusted device is misplaced).
       *
       * If the calling account had been granted `role`, emits a {RoleRevoked}
       * event.
       *
       * Requirements:
       *
       * - the caller must be `account`.
       */
      function renounceRole(bytes32 role, address account) external;
  }
  
  // File: @openzeppelin/contracts/access/IAccessControlEnumerable.sol
  
  
  // OpenZeppelin Contracts v4.4.1 (access/IAccessControlEnumerable.sol)
  
  pragma solidity ^0.8.0;
  
  /**
   * @dev External interface of AccessControlEnumerable declared to support ERC165 detection.
   */
  interface IAccessControlEnumerable is IAccessControl {
      /**
       * @dev Returns one of the accounts that have `role`. `index` must be a
       * value between 0 and {getRoleMemberCount}, non-inclusive.
       *
       * Role bearers are not sorted in any particular way, and their ordering may
       * change at any point.
       *
       * WARNING: When using {getRoleMember} and {getRoleMemberCount}, make sure
       * you perform all queries on the same block. See the following
       * https://forum.openzeppelin.com/t/iterating-over-elements-on-enumerableset-in-openzeppelin-contracts/2296[forum post]
       * for more information.
       */
      function getRoleMember(bytes32 role, uint256 index) external view returns (address);
  
      /**
       * @dev Returns the number of accounts that have `role`. Can be used
       * together with {getRoleMember} to enumerate all bearers of a role.
       */
      function getRoleMemberCount(bytes32 role) external view returns (uint256);
  }
  
  // File: @openzeppelin/contracts/utils/math/Math.sol
  
  
  // OpenZeppelin Contracts (last updated v4.8.0) (utils/math/Math.sol)
  
  pragma solidity ^0.8.0;
  
  /**
   * @dev Standard math utilities missing in the Solidity language.
   */
  library Math {
      enum Rounding {
          Down, // Toward negative infinity
          Up, // Toward infinity
          Zero // Toward zero
      }
  
      /**
       * @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 up instead
       * of rounding down.
       */
      function ceilDiv(uint256 a, uint256 b) internal pure returns (uint256) {
          // (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; // Least significant 256 bits of the product
              uint256 prod1; // Most significant 256 bits of the product
              assembly {
                  let mm := mulmod(x, y, not(0))
                  prod0 := mul(x, y)
                  prod1 := sub(sub(mm, prod0), lt(mm, prod0))
              }
  
              // Handle non-overflow cases, 256 by 256 division.
              if (prod1 == 0) {
                  return prod0 / denominator;
              }
  
              // Make sure the result is less than 2^256. Also prevents denominator == 0.
              require(denominator > prod1);
  
              ///////////////////////////////////////////////
              // 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.
  
              // Does not overflow because the denominator cannot be zero at this stage in the function.
              uint256 twos = denominator & (~denominator + 1);
              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 (rounding == Rounding.Up && 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 down.
       *
       * 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 + (rounding == Rounding.Up && result * result < a ? 1 : 0);
          }
      }
  
      /**
       * @dev Return the log in base 2, rounded down, of a positive value.
       * 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 + (rounding == Rounding.Up && 1 << result < value ? 1 : 0);
          }
      }
  
      /**
       * @dev Return the log in base 10, rounded down, of a positive value.
       * 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 + (rounding == Rounding.Up && 10**result < value ? 1 : 0);
          }
      }
  
      /**
       * @dev Return the log in base 256, rounded down, of a positive value.
       * 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 10, 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 + (rounding == Rounding.Up && 1 << (result * 8) < value ? 1 : 0);
          }
      }
  }
  
  // File: @openzeppelin/contracts/utils/Strings.sol
  
  
  // OpenZeppelin Contracts (last updated v4.8.0) (utils/Strings.sol)
  
  pragma solidity ^0.8.0;
  
  /**
   * @dev String operations.
   */
  library Strings {
      bytes16 private constant _SYMBOLS = "0123456789abcdef";
      uint8 private constant _ADDRESS_LENGTH = 20;
  
      /**
       * @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), _SYMBOLS))
                  }
                  value /= 10;
                  if (value == 0) break;
              }
              return buffer;
          }
      }
  
      /**
       * @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) {
          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] = _SYMBOLS[value & 0xf];
              value >>= 4;
          }
          require(value == 0, "Strings: hex length insufficient");
          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);
      }
  }
  
  // File: @openzeppelin/contracts/utils/introspection/IERC165.sol
  
  
  // OpenZeppelin Contracts v4.4.1 (utils/introspection/IERC165.sol)
  
  pragma solidity ^0.8.0;
  
  /**
   * @dev Interface of the ERC165 standard, as defined in the
   * https://eips.ethereum.org/EIPS/eip-165[EIP].
   *
   * Implementers can declare support of contract interfaces, which can then be
   * queried by others ({ERC165Checker}).
   *
   * For an implementation, see {ERC165}.
   */
  interface IERC165 {
      /**
       * @dev Returns true if this contract implements the interface defined by
       * `interfaceId`. See the corresponding
       * https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified[EIP section]
       * to learn more about how these ids are created.
       *
       * This function call must use less than 30 000 gas.
       */
      function supportsInterface(bytes4 interfaceId) external view returns (bool);
  }
  
  // File: @openzeppelin/contracts/utils/introspection/ERC165.sol
  
  
  // OpenZeppelin Contracts v4.4.1 (utils/introspection/ERC165.sol)
  
  pragma solidity ^0.8.0;
  
  /**
   * @dev Implementation of the {IERC165} interface.
   *
   * Contracts that want to implement ERC165 should inherit from this contract and override {supportsInterface} to check
   * for the additional interface id that will be supported. For example:
   *
   * ```solidity
   * function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
   *     return interfaceId == type(MyInterface).interfaceId || super.supportsInterface(interfaceId);
   * }
   * ```
   *
   * Alternatively, {ERC165Storage} provides an easier to use but more expensive implementation.
   */
  abstract contract ERC165 is IERC165 {
      /**
       * @dev See {IERC165-supportsInterface}.
       */
      function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
          return interfaceId == type(IERC165).interfaceId;
      }
  }
  
  // File: @openzeppelin/contracts/access/AccessControl.sol
  
  
  // OpenZeppelin Contracts (last updated v4.8.0) (access/AccessControl.sol)
  
  pragma solidity ^0.8.0;
  
  
  
  
  /**
   * @dev Contract module that allows children to implement role-based access
   * control mechanisms. This is a lightweight version that doesn't allow enumerating role
   * members except through off-chain means by accessing the contract event logs. Some
   * applications may benefit from on-chain enumerability, for those cases see
   * {AccessControlEnumerable}.
   *
   * Roles are referred to by their `bytes32` identifier. These should be exposed
   * in the external API and be unique. The best way to achieve this is by
   * using `public constant` hash digests:
   *
   * ```
   * bytes32 public constant MY_ROLE = keccak256("MY_ROLE");
   * ```
   *
   * Roles can be used to represent a set of permissions. To restrict access to a
   * function call, use {hasRole}:
   *
   * ```
   * function foo() public {
   *     require(hasRole(MY_ROLE, msg.sender));
   *     ...
   * }
   * ```
   *
   * Roles can be granted and revoked dynamically via the {grantRole} and
   * {revokeRole} functions. Each role has an associated admin role, and only
   * accounts that have a role's admin role can call {grantRole} and {revokeRole}.
   *
   * By default, the admin role for all roles is `DEFAULT_ADMIN_ROLE`, which means
   * that only accounts with this role will be able to grant or revoke other
   * roles. More complex role relationships can be created by using
   * {_setRoleAdmin}.
   *
   * WARNING: The `DEFAULT_ADMIN_ROLE` is also its own admin: it has permission to
   * grant and revoke this role. Extra precautions should be taken to secure
   * accounts that have been granted it.
   */
  abstract contract AccessControl is Context, IAccessControl, ERC165 {
      struct RoleData {
          mapping(address => bool) members;
          bytes32 adminRole;
      }
  
      mapping(bytes32 => RoleData) private _roles;
  
      bytes32 public constant DEFAULT_ADMIN_ROLE = 0x00;
  
      /**
       * @dev Modifier that checks that an account has a specific role. Reverts
       * with a standardized message including the required role.
       *
       * The format of the revert reason is given by the following regular expression:
       *
       *  /^AccessControl: account (0x[0-9a-f]{40}) is missing role (0x[0-9a-f]{64})$/
       *
       * _Available since v4.1._
       */
      modifier onlyRole(bytes32 role) {
          _checkRole(role);
          _;
      }
  
      /**
       * @dev See {IERC165-supportsInterface}.
       */
      function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
          return interfaceId == type(IAccessControl).interfaceId || super.supportsInterface(interfaceId);
      }
  
      /**
       * @dev Returns `true` if `account` has been granted `role`.
       */
      function hasRole(bytes32 role, address account) public view virtual override returns (bool) {
          return _roles[role].members[account];
      }
  
      /**
       * @dev Revert with a standard message if `_msgSender()` is missing `role`.
       * Overriding this function changes the behavior of the {onlyRole} modifier.
       *
       * Format of the revert message is described in {_checkRole}.
       *
       * _Available since v4.6._
       */
      function _checkRole(bytes32 role) internal view virtual {
          _checkRole(role, _msgSender());
      }
  
      /**
       * @dev Revert with a standard message if `account` is missing `role`.
       *
       * The format of the revert reason is given by the following regular expression:
       *
       *  /^AccessControl: account (0x[0-9a-f]{40}) is missing role (0x[0-9a-f]{64})$/
       */
      function _checkRole(bytes32 role, address account) internal view virtual {
          if (!hasRole(role, account)) {
              revert(
                  string(
                      abi.encodePacked(
                          "AccessControl: account ",
                          Strings.toHexString(account),
                          " is missing role ",
                          Strings.toHexString(uint256(role), 32)
                      )
                  )
              );
          }
      }
  
      /**
       * @dev Returns the admin role that controls `role`. See {grantRole} and
       * {revokeRole}.
       *
       * To change a role's admin, use {_setRoleAdmin}.
       */
      function getRoleAdmin(bytes32 role) public view virtual override returns (bytes32) {
          return _roles[role].adminRole;
      }
  
      /**
       * @dev Grants `role` to `account`.
       *
       * If `account` had not been already granted `role`, emits a {RoleGranted}
       * event.
       *
       * Requirements:
       *
       * - the caller must have ``role``'s admin role.
       *
       * May emit a {RoleGranted} event.
       */
      function grantRole(bytes32 role, address account) public virtual override onlyRole(getRoleAdmin(role)) {
          _grantRole(role, account);
      }
  
      /**
       * @dev Revokes `role` from `account`.
       *
       * If `account` had been granted `role`, emits a {RoleRevoked} event.
       *
       * Requirements:
       *
       * - the caller must have ``role``'s admin role.
       *
       * May emit a {RoleRevoked} event.
       */
      function revokeRole(bytes32 role, address account) public virtual override onlyRole(getRoleAdmin(role)) {
          _revokeRole(role, account);
      }
  
      /**
       * @dev Revokes `role` from the calling account.
       *
       * Roles are often managed via {grantRole} and {revokeRole}: this function's
       * purpose is to provide a mechanism for accounts to lose their privileges
       * if they are compromised (such as when a trusted device is misplaced).
       *
       * If the calling account had been revoked `role`, emits a {RoleRevoked}
       * event.
       *
       * Requirements:
       *
       * - the caller must be `account`.
       *
       * May emit a {RoleRevoked} event.
       */
      function renounceRole(bytes32 role, address account) public virtual override {
          require(account == _msgSender(), "AccessControl: can only renounce roles for self");
  
          _revokeRole(role, account);
      }
  
      /**
       * @dev Grants `role` to `account`.
       *
       * If `account` had not been already granted `role`, emits a {RoleGranted}
       * event. Note that unlike {grantRole}, this function doesn't perform any
       * checks on the calling account.
       *
       * May emit a {RoleGranted} event.
       *
       * [WARNING]
       * ====
       * This function should only be called from the constructor when setting
       * up the initial roles for the system.
       *
       * Using this function in any other way is effectively circumventing the admin
       * system imposed by {AccessControl}.
       * ====
       *
       * NOTE: This function is deprecated in favor of {_grantRole}.
       */
      function _setupRole(bytes32 role, address account) internal virtual {
          _grantRole(role, account);
      }
  
      /**
       * @dev Sets `adminRole` as ``role``'s admin role.
       *
       * Emits a {RoleAdminChanged} event.
       */
      function _setRoleAdmin(bytes32 role, bytes32 adminRole) internal virtual {
          bytes32 previousAdminRole = getRoleAdmin(role);
          _roles[role].adminRole = adminRole;
          emit RoleAdminChanged(role, previousAdminRole, adminRole);
      }
  
      /**
       * @dev Grants `role` to `account`.
       *
       * Internal function without access restriction.
       *
       * May emit a {RoleGranted} event.
       */
      function _grantRole(bytes32 role, address account) internal virtual {
          if (!hasRole(role, account)) {
              _roles[role].members[account] = true;
              emit RoleGranted(role, account, _msgSender());
          }
      }
  
      /**
       * @dev Revokes `role` from `account`.
       *
       * Internal function without access restriction.
       *
       * May emit a {RoleRevoked} event.
       */
      function _revokeRole(bytes32 role, address account) internal virtual {
          if (hasRole(role, account)) {
              _roles[role].members[account] = false;
              emit RoleRevoked(role, account, _msgSender());
          }
      }
  }
  
  // File: @openzeppelin/contracts/utils/structs/EnumerableSet.sol
  
  
  // OpenZeppelin Contracts (last updated v4.8.0) (utils/structs/EnumerableSet.sol)
  // This file was procedurally generated from scripts/generate/templates/EnumerableSet.js.
  
  pragma solidity ^0.8.0;
  
  /**
   * @dev Library for managing
   * https://en.wikipedia.org/wiki/Set_(abstract_data_type)[sets] of primitive
   * types.
   *
   * Sets have the following properties:
   *
   * - Elements are added, removed, and checked for existence in constant time
   * (O(1)).
   * - Elements are enumerated in O(n). No guarantees are made on the ordering.
   *
   * ```
   * contract Example {
   *     // Add the library methods
   *     using EnumerableSet for EnumerableSet.AddressSet;
   *
   *     // Declare a set state variable
   *     EnumerableSet.AddressSet private mySet;
   * }
   * ```
   *
   * As of v3.3.0, sets of type `bytes32` (`Bytes32Set`), `address` (`AddressSet`)
   * and `uint256` (`UintSet`) are supported.
   *
   * [WARNING]
   * ====
   * Trying to delete such a structure from storage will likely result in data corruption, rendering the structure
   * unusable.
   * See https://github.com/ethereum/solidity/pull/11843[ethereum/solidity#11843] for more info.
   *
   * In order to clean an EnumerableSet, you can either remove all elements one by one or create a fresh instance using an
   * array of EnumerableSet.
   * ====
   */
  library EnumerableSet {
      // To implement this library for multiple types with as little code
      // repetition as possible, we write it in terms of a generic Set type with
      // bytes32 values.
      // The Set implementation uses private functions, and user-facing
      // implementations (such as AddressSet) are just wrappers around the
      // underlying Set.
      // This means that we can only create new EnumerableSets for types that fit
      // in bytes32.
  
      struct Set {
          // Storage of set values
          bytes32[] _values;
          // Position of the value in the `values` array, plus 1 because index 0
          // means a value is not in the set.
          mapping(bytes32 => uint256) _indexes;
      }
  
      /**
       * @dev Add a value to a set. O(1).
       *
       * Returns true if the value was added to the set, that is if it was not
       * already present.
       */
      function _add(Set storage set, bytes32 value) private returns (bool) {
          if (!_contains(set, value)) {
              set._values.push(value);
              // The value is stored at length-1, but we add 1 to all indexes
              // and use 0 as a sentinel value
              set._indexes[value] = set._values.length;
              return true;
          } else {
              return false;
          }
      }
  
      /**
       * @dev Removes a value from a set. O(1).
       *
       * Returns true if the value was removed from the set, that is if it was
       * present.
       */
      function _remove(Set storage set, bytes32 value) private returns (bool) {
          // We read and store the value's index to prevent multiple reads from the same storage slot
          uint256 valueIndex = set._indexes[value];
  
          if (valueIndex != 0) {
              // Equivalent to contains(set, value)
              // To delete an element from the _values array in O(1), we swap the element to delete with the last one in
              // the array, and then remove the last element (sometimes called as 'swap and pop').
              // This modifies the order of the array, as noted in {at}.
  
              uint256 toDeleteIndex = valueIndex - 1;
              uint256 lastIndex = set._values.length - 1;
  
              if (lastIndex != toDeleteIndex) {
                  bytes32 lastValue = set._values[lastIndex];
  
                  // Move the last value to the index where the value to delete is
                  set._values[toDeleteIndex] = lastValue;
                  // Update the index for the moved value
                  set._indexes[lastValue] = valueIndex; // Replace lastValue's index to valueIndex
              }
  
              // Delete the slot where the moved value was stored
              set._values.pop();
  
              // Delete the index for the deleted slot
              delete set._indexes[value];
  
              return true;
          } else {
              return false;
          }
      }
  
      /**
       * @dev Returns true if the value is in the set. O(1).
       */
      function _contains(Set storage set, bytes32 value) private view returns (bool) {
          return set._indexes[value] != 0;
      }
  
      /**
       * @dev Returns the number of values on the set. O(1).
       */
      function _length(Set storage set) private view returns (uint256) {
          return set._values.length;
      }
  
      /**
       * @dev Returns the value stored at position `index` in the set. O(1).
       *
       * Note that there are no guarantees on the ordering of values inside the
       * array, and it may change when more values are added or removed.
       *
       * Requirements:
       *
       * - `index` must be strictly less than {length}.
       */
      function _at(Set storage set, uint256 index) private view returns (bytes32) {
          return set._values[index];
      }
  
      /**
       * @dev Return the entire set in an array
       *
       * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
       * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
       * this function has an unbounded cost, and using it as part of a state-changing function may render the function
       * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
       */
      function _values(Set storage set) private view returns (bytes32[] memory) {
          return set._values;
      }
  
      // Bytes32Set
  
      struct Bytes32Set {
          Set _inner;
      }
  
      /**
       * @dev Add a value to a set. O(1).
       *
       * Returns true if the value was added to the set, that is if it was not
       * already present.
       */
      function add(Bytes32Set storage set, bytes32 value) internal returns (bool) {
          return _add(set._inner, value);
      }
  
      /**
       * @dev Removes a value from a set. O(1).
       *
       * Returns true if the value was removed from the set, that is if it was
       * present.
       */
      function remove(Bytes32Set storage set, bytes32 value) internal returns (bool) {
          return _remove(set._inner, value);
      }
  
      /**
       * @dev Returns true if the value is in the set. O(1).
       */
      function contains(Bytes32Set storage set, bytes32 value) internal view returns (bool) {
          return _contains(set._inner, value);
      }
  
      /**
       * @dev Returns the number of values in the set. O(1).
       */
      function length(Bytes32Set storage set) internal view returns (uint256) {
          return _length(set._inner);
      }
  
      /**
       * @dev Returns the value stored at position `index` in the set. O(1).
       *
       * Note that there are no guarantees on the ordering of values inside the
       * array, and it may change when more values are added or removed.
       *
       * Requirements:
       *
       * - `index` must be strictly less than {length}.
       */
      function at(Bytes32Set storage set, uint256 index) internal view returns (bytes32) {
          return _at(set._inner, index);
      }
  
      /**
       * @dev Return the entire set in an array
       *
       * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
       * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
       * this function has an unbounded cost, and using it as part of a state-changing function may render the function
       * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
       */
      function values(Bytes32Set storage set) internal view returns (bytes32[] memory) {
          bytes32[] memory store = _values(set._inner);
          bytes32[] memory result;
  
          /// @solidity memory-safe-assembly
          assembly {
              result := store
          }
  
          return result;
      }
  
      // AddressSet
  
      struct AddressSet {
          Set _inner;
      }
  
      /**
       * @dev Add a value to a set. O(1).
       *
       * Returns true if the value was added to the set, that is if it was not
       * already present.
       */
      function add(AddressSet storage set, address value) internal returns (bool) {
          return _add(set._inner, bytes32(uint256(uint160(value))));
      }
  
      /**
       * @dev Removes a value from a set. O(1).
       *
       * Returns true if the value was removed from the set, that is if it was
       * present.
       */
      function remove(AddressSet storage set, address value) internal returns (bool) {
          return _remove(set._inner, bytes32(uint256(uint160(value))));
      }
  
      /**
       * @dev Returns true if the value is in the set. O(1).
       */
      function contains(AddressSet storage set, address value) internal view returns (bool) {
          return _contains(set._inner, bytes32(uint256(uint160(value))));
      }
  
      /**
       * @dev Returns the number of values in the set. O(1).
       */
      function length(AddressSet storage set) internal view returns (uint256) {
          return _length(set._inner);
      }
  
      /**
       * @dev Returns the value stored at position `index` in the set. O(1).
       *
       * Note that there are no guarantees on the ordering of values inside the
       * array, and it may change when more values are added or removed.
       *
       * Requirements:
       *
       * - `index` must be strictly less than {length}.
       */
      function at(AddressSet storage set, uint256 index) internal view returns (address) {
          return address(uint160(uint256(_at(set._inner, index))));
      }
  
      /**
       * @dev Return the entire set in an array
       *
       * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
       * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
       * this function has an unbounded cost, and using it as part of a state-changing function may render the function
       * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
       */
      function values(AddressSet storage set) internal view returns (address[] memory) {
          bytes32[] memory store = _values(set._inner);
          address[] memory result;
  
          /// @solidity memory-safe-assembly
          assembly {
              result := store
          }
  
          return result;
      }
  
      // UintSet
  
      struct UintSet {
          Set _inner;
      }
  
      /**
       * @dev Add a value to a set. O(1).
       *
       * Returns true if the value was added to the set, that is if it was not
       * already present.
       */
      function add(UintSet storage set, uint256 value) internal returns (bool) {
          return _add(set._inner, bytes32(value));
      }
  
      /**
       * @dev Removes a value from a set. O(1).
       *
       * Returns true if the value was removed from the set, that is if it was
       * present.
       */
      function remove(UintSet storage set, uint256 value) internal returns (bool) {
          return _remove(set._inner, bytes32(value));
      }
  
      /**
       * @dev Returns true if the value is in the set. O(1).
       */
      function contains(UintSet storage set, uint256 value) internal view returns (bool) {
          return _contains(set._inner, bytes32(value));
      }
  
      /**
       * @dev Returns the number of values in the set. O(1).
       */
      function length(UintSet storage set) internal view returns (uint256) {
          return _length(set._inner);
      }
  
      /**
       * @dev Returns the value stored at position `index` in the set. O(1).
       *
       * Note that there are no guarantees on the ordering of values inside the
       * array, and it may change when more values are added or removed.
       *
       * Requirements:
       *
       * - `index` must be strictly less than {length}.
       */
      function at(UintSet storage set, uint256 index) internal view returns (uint256) {
          return uint256(_at(set._inner, index));
      }
  
      /**
       * @dev Return the entire set in an array
       *
       * WARNING: This operation will copy the entire storage to memory, which can be quite expensive. This is designed
       * to mostly be used by view accessors that are queried without any gas fees. Developers should keep in mind that
       * this function has an unbounded cost, and using it as part of a state-changing function may render the function
       * uncallable if the set grows to a point where copying to memory consumes too much gas to fit in a block.
       */
      function values(UintSet storage set) internal view returns (uint256[] memory) {
          bytes32[] memory store = _values(set._inner);
          uint256[] memory result;
  
          /// @solidity memory-safe-assembly
          assembly {
              result := store
          }
  
          return result;
      }
  }
  
  // File: @openzeppelin/contracts/access/AccessControlEnumerable.sol
  
  
  // OpenZeppelin Contracts (last updated v4.5.0) (access/AccessControlEnumerable.sol)
  
  pragma solidity ^0.8.0;
  
  
  
  /**
   * @dev Extension of {AccessControl} that allows enumerating the members of each role.
   */
  abstract contract AccessControlEnumerable is IAccessControlEnumerable, AccessControl {
      using EnumerableSet for EnumerableSet.AddressSet;
  
      mapping(bytes32 => EnumerableSet.AddressSet) private _roleMembers;
  
      /**
       * @dev See {IERC165-supportsInterface}.
       */
      function supportsInterface(bytes4 interfaceId) public view virtual override returns (bool) {
          return interfaceId == type(IAccessControlEnumerable).interfaceId || super.supportsInterface(interfaceId);
      }
  
      /**
       * @dev Returns one of the accounts that have `role`. `index` must be a
       * value between 0 and {getRoleMemberCount}, non-inclusive.
       *
       * Role bearers are not sorted in any particular way, and their ordering may
       * change at any point.
       *
       * WARNING: When using {getRoleMember} and {getRoleMemberCount}, make sure
       * you perform all queries on the same block. See the following
       * https://forum.openzeppelin.com/t/iterating-over-elements-on-enumerableset-in-openzeppelin-contracts/2296[forum post]
       * for more information.
       */
      function getRoleMember(bytes32 role, uint256 index) public view virtual override returns (address) {
          return _roleMembers[role].at(index);
      }
  
      /**
       * @dev Returns the number of accounts that have `role`. Can be used
       * together with {getRoleMember} to enumerate all bearers of a role.
       */
      function getRoleMemberCount(bytes32 role) public view virtual override returns (uint256) {
          return _roleMembers[role].length();
      }
  
      /**
       * @dev Overload {_grantRole} to track enumerable memberships
       */
      function _grantRole(bytes32 role, address account) internal virtual override {
          super._grantRole(role, account);
          _roleMembers[role].add(account);
      }
  
      /**
       * @dev Overload {_revokeRole} to track enumerable memberships
       */
      function _revokeRole(bytes32 role, address account) internal virtual override {
          super._revokeRole(role, account);
          _roleMembers[role].remove(account);
      }
  }
  
  // File: @openzeppelin/contracts/token/ERC20/presets/ERC20PresetMinterPauser.sol
  
  
  // OpenZeppelin Contracts (last updated v4.5.0) (token/ERC20/presets/ERC20PresetMinterPauser.sol)
  
  pragma solidity ^0.8.0;
  
  
  
  
  
  /**
   * @dev {ERC20} token, including:
   *
   *  - ability for holders to burn (destroy) their tokens
   *  - a minter role that allows for token minting (creation)
   *  - a pauser role that allows to stop all token transfers
   *
   * This contract uses {AccessControl} to lock permissioned functions using the
   * different roles - head to its documentation for details.
   *
   * The account that deploys the contract will be granted the minter and pauser
   * roles, as well as the default admin role, which will let it grant both minter
   * and pauser roles to other accounts.
   *
   * _Deprecated in favor of https://wizard.openzeppelin.com/[Contracts Wizard]._
   */
  contract ERC20PresetMinterPauser is Context, AccessControlEnumerable, ERC20Burnable, ERC20Pausable {
      bytes32 public constant MINTER_ROLE = keccak256("MINTER_ROLE");
      bytes32 public constant PAUSER_ROLE = keccak256("PAUSER_ROLE");
  
      /**
       * @dev Grants `DEFAULT_ADMIN_ROLE`, `MINTER_ROLE` and `PAUSER_ROLE` to the
       * account that deploys the contract.
       *
       * See {ERC20-constructor}.
       */
      constructor(string memory name, string memory symbol) ERC20(name, symbol) {
          _setupRole(DEFAULT_ADMIN_ROLE, _msgSender());
  
          _setupRole(MINTER_ROLE, _msgSender());
          _setupRole(PAUSER_ROLE, _msgSender());
      }
  
      /**
       * @dev Creates `amount` new tokens for `to`.
       *
       * See {ERC20-_mint}.
       *
       * Requirements:
       *
       * - the caller must have the `MINTER_ROLE`.
       */
      function mint(address to, uint256 amount) public virtual {
          require(hasRole(MINTER_ROLE, _msgSender()), "ERC20PresetMinterPauser: must have minter role to mint");
          _mint(to, amount);
      }
  
      /**
       * @dev Pauses all token transfers.
       *
       * See {ERC20Pausable} and {Pausable-_pause}.
       *
       * Requirements:
       *
       * - the caller must have the `PAUSER_ROLE`.
       */
      function pause() public virtual {
          require(hasRole(PAUSER_ROLE, _msgSender()), "ERC20PresetMinterPauser: must have pauser role to pause");
          _pause();
      }
  
      /**
       * @dev Unpauses all token transfers.
       *
       * See {ERC20Pausable} and {Pausable-_unpause}.
       *
       * Requirements:
       *
       * - the caller must have the `PAUSER_ROLE`.
       */
      function unpause() public virtual {
          require(hasRole(PAUSER_ROLE, _msgSender()), "ERC20PresetMinterPauser: must have pauser role to unpause");
          _unpause();
      }
  
      function _beforeTokenTransfer(
          address from,
          address to,
          uint256 amount
      ) internal virtual override(ERC20, ERC20Pausable) {
          super._beforeTokenTransfer(from, to, amount);
      }
  }
  
  // File: contracts/CERsCoin.sol
  
  
  pragma solidity ^0.8.4;
  
  contract CERsCoin is ERC20PresetMinterPauser {
      constructor() ERC20PresetMinterPauser("CERs Coin", "CRC") {
          _mint(msg.sender, 100000000000000 * (10 ** uint256(decimals())));
      }
  
      function mint(address, uint256) public virtual override {
          revert("Minting disabled - no more tokens can be minted!");
      }
  }