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 CPP):

Solution:
#include<stdio.h>
 
int main(void){
  int r;
  scanf("%d",&r);
  printf("%lf\n", 2*3.14159265*r);
}