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Description

给定圆的半径r，求圆的面积。

Format

Input

输入包含一个整数r，表示圆的半径。

Output

输出一行，包含一个实数，四舍五入保留小数点后7位，表示圆的面积。

Samples

4

50.2654825 

Limitation

1s, 1024KiB for each test case.