Problem: 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}.

Examples

Input

1


Output

6.28318530717958623200


Input

73


Output

458.67252742410977361942

Solution (in JAVA):

Solution:
import 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
		int b = sc.nextInt();
      System.out.println(b*2*Math.PI);
	}
}