# Pie Are Squared

#4N_RedWings1
Limits 1s, 512 MB

Given the radius of a circle, calculate and print its area.

The area of a circle can be computed using the following formula:

$A = \pi r^2$

For pi, you can use 3.141592653589793, or acos(-1).

## Input

The input will contain one floating-point number $r$ ($0 < r < 2000$).

## Output

Print the area of the circle (accurate to $10^{-4}$).

## Sample

InputOutput
2

12.5663706144