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<bits/stdc++.h>
#define ll long long 
#define mp make_pair 
#define pb push_back 
#define F first 
#define S second 
#define f(i,n) for(int i=0;i<n;i++) 
#define fr(i,a,b) for(int i=a;i<b;i++) 

using namespace std;

void test(){
	double x;
	cin>>x;
	x = 2*x;
	x = x*(3.14159);
	cout<<x<<"\n";
}

int main(){
	int t=1;
//	cin>>t;
	while(t--){
		test();
	}
}