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 PHP (7.4.4) (judge verdict: Accepted)

<?php
//error_reporting(0);
//$N = (int)trim(fgets(STDIN));
$R = trim(fgets(STDIN));
//list($a,$b,$c) = array_map('intval',explode(" ",trim(fgets(STDIN))));
//$s = trim(fgets(STDIN));
//$a = array_map('intval',explode(" ",trim(fgets(STDIN))));


printf("%f\n",($R*2)*M_PI);