Problem: 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}.

Examples

Input

1


Output

6.28318530717958623200


Input

73


Output

458.67252742410977361942

Solution (in PYTHON):

Solution:
import math
print math.pi * 2 * float(raw_input())