Problem:
Score : 100 points

Problem Statement

Print the circumference of a circle of radius R.

Constraints

1 \leq R \leq 100

All values in input are integers.

Input

Input is given from Standard Input in the following format:

R

Output

Print the circumference of the circle.
Your output is considered correct if and only if its absolute or relative error from our answer is at most 10^{-2}.

Sample Input 1

1

Sample Output 1

6.28318530717958623200

Since we accept an absolute or relative error of at most 10^{-2}, 6.28 is also an acceptable output, but 6 is not.

Sample Input 2

73

Sample Output 2

458.67252742410977361942

Solution in Java (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.*;


public class Main {
    public static void main(String[] args) {
      
      Scanner sc = new Scanner(System.in);
      double r = Double.parseDouble(sc.next());
      
      System.out.println(calCircumference(r));
      
    }
  private static double calCircumference(double r) {
        return 2 * Math.PI * r;
    }
}