
import java.math.BigDecimal;
import java.math.RoundingMode;
import java.util.Scanner;

public class Main {

  public static void main(String[] args) {

    Scanner sc = new Scanner(System.in);
    // スペース区切りの整数の入力
    BigDecimal R = new BigDecimal(sc.nextInt());
    BigDecimal S = R.multiply(new BigDecimal(2)).setScale(100, RoundingMode.HALF_UP);

    System.out.println(S.multiply(new BigDecimal("3.1415")).setScale(100, RoundingMode.HALF_UP));
  }
} import java.math.BigDecimal; BigDecimal java.math import java.math.RoundingMode; RoundingMode java.math import java.util.Scanner; Scanner java.util public class Main {

  public static void main(String[] args) {

    Scanner sc = new Scanner(System.in);
    // スペース区切りの整数の入力
    BigDecimal R = new BigDecimal(sc.nextInt());
    BigDecimal S = R.multiply(new BigDecimal(2)).setScale(100, RoundingMode.HALF_UP);

    System.out.println(S.multiply(new BigDecimal("3.1415")).setScale(100, RoundingMode.HALF_UP));
  }
} Main public static void main(String[] args) {

    Scanner sc = new Scanner(System.in);
    // スペース区切りの整数の入力
    BigDecimal R = new BigDecimal(sc.nextInt());
    BigDecimal S = R.multiply(new BigDecimal(2)).setScale(100, RoundingMode.HALF_UP);

    System.out.println(S.multiply(new BigDecimal("3.1415")).setScale(100, RoundingMode.HALF_UP));
  } main {

    Scanner sc = new Scanner(System.in);
    // スペース区切りの整数の入力
    BigDecimal R = new BigDecimal(sc.nextInt());
    BigDecimal S = R.multiply(new BigDecimal(2)).setScale(100, RoundingMode.HALF_UP);

    System.out.println(S.multiply(new BigDecimal("3.1415")).setScale(100, RoundingMode.HALF_UP));
  } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) BigDecimal R = new BigDecimal(sc.nextInt()); R new BigDecimal(sc.nextInt()) BigDecimal S = R.multiply(new BigDecimal(2)).setScale(100, RoundingMode.HALF_UP); S R.multiply(new BigDecimal(2)).setScale(100, RoundingMode.HALF_UP) R.multiply(new BigDecimal(2)).setScale R.multiply(new BigDecimal(2)) R.multiply R new BigDecimal(2) 100 RoundingMode.HALF_UP RoundingMode RoundingMode.HALF_UP System.out.println(S.multiply(new BigDecimal("3.1415")).setScale(100, RoundingMode.HALF_UP)) System.out.println System.out System System.out S.multiply(new BigDecimal("3.1415")).setScale(100, RoundingMode.HALF_UP) S.multiply(new BigDecimal("3.1415")).setScale S.multiply(new BigDecimal("3.1415")) S.multiply S new BigDecimal("3.1415") 100 RoundingMode.HALF_UP RoundingMode RoundingMode.HALF_UP String[] args args public class Main {

  public static void main(String[] args) {

    Scanner sc = new Scanner(System.in);
    // スペース区切りの整数の入力
    BigDecimal R = new BigDecimal(sc.nextInt());
    BigDecimal S = R.multiply(new BigDecimal(2)).setScale(100, RoundingMode.HALF_UP);

    System.out.println(S.multiply(new BigDecimal("3.1415")).setScale(100, RoundingMode.HALF_UP));
  }
} public class Main {

  public static void main(String[] args) {

    Scanner sc = new Scanner(System.in);
    // スペース区切りの整数の入力
    BigDecimal R = new BigDecimal(sc.nextInt());
    BigDecimal S = R.multiply(new BigDecimal(2)).setScale(100, RoundingMode.HALF_UP);

    System.out.println(S.multiply(new BigDecimal("3.1415")).setScale(100, RoundingMode.HALF_UP));
  }
} Main

import java.math.BigDecimal;
import java.math.RoundingMode;
import java.util.Scanner;

public class Main {

  public static void main(String[] args) {

    Scanner sc = new Scanner(System.in);
    // スペース区切りの整数の入力
    BigDecimal R = new BigDecimal(sc.nextInt());
    BigDecimal S = R.multiply(new BigDecimal(2)).setScale(100, RoundingMode.HALF_UP);

    System.out.println(S.multiply(new BigDecimal("3.1415")).setScale(100, RoundingMode.HALF_UP));
  }
}
