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 JavaScript (Node.js 12.16.1) (judge verdict: Accepted)

process.stdin.resume();
process.stdin.setEncoding('utf8');
// Your code here!
 
const gcdArr = function(arr) {
  let gcdres = gcd(arr[0], arr[1])
  for (let i=2; i<arr.length; i++) {
    gcdres = gcd(gcdres, arr[i])
  }
  return gcdres
}
 
function gcd_impl(n,m) {
        for( let i = 0; i < 10; ++i ) {
                let t = n - m;
                let q = m > t;
                n = q ? m : t;
                m = q ? t : m;
                if( m == 0 ) { return n; }
        }
        return gcd_impl( m, n % m );
}
 
function gcd( n, m ) {
        return n > m ? gcd_impl( n, m ) : gcd_impl( m, n );
}
 
const Main = (p)=>{
	// 1行目がinput[0], 2行目がinput[1], …に入る
	
	let t = parseInt(p);//p.split(" ").map(Number);
	//文字列から10進数に変換するときはparseIntを使います
	//出力
	
	console.log(p*2*3.14115);
}
//*この行以降は編集しないでください（標準入出力から一度に読み込み、Mainを呼び出します）
Main(require("fs").readFileSync("/dev/stdin", "utf8"));