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 C (GCC 9.2.1) (judge verdict: Accepted)

#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <string.h>
#define yes "Yes\n"
#define no "No\n"
int r;
//int m,n;
//int i,j,k,l;
//int a,b,c,d,e,f,g;
//int sum,total;
//long long int ;
//float ;
//double ;
//char a[101],b[101],s[101],t[101],u[101];
int main(void){
    scanf("%d",&r);
    printf("%f",2*r*M_PI);
    return 0;
}