Problem Statement

The circumference of a circle is the distance around the circle. To calculate the circumference, we use the following formula:

\(2 * \pi * radius\)

Given the radius R, make a program that will print the circumference.

Note: Use the following code to import \(\pi\) :

import math

pi = math.pi

Constraints

• R is a float between 1 and 100

Input

Input is in the following format:

R

Output

Print the circumference as a float:

Samples

Sample 1

Sample 2

Sample 3