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# (.NET Core 3.1.201) (judge verdict: Accepted)

using System;
namespace kozaiyApp
{
    public class A
    {
        static void Main()
        {
            // 2 * 半径 * 円周率: Math.PI
            int R = int.Parse(Console.ReadLine());
            double ans = 2 * R * Math.PI;
            Console.WriteLine(ans);
        }
    }
}