# Build a Fence

Time Limit: 2000/1000 MS (Java/Others)

Memory Limit: 32768/32768 K (Java/Others)

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## Description

There is a wall in your backyard. It is so long that you can’t see its endpoints. You want to build a fence of length L such that the area enclosed between the wall and the fence is maximized. The fence can be of arbitrary shape, but only its two endpoints may touch the wall.

## Input

The input consists of several test cases.
For every test case, there is only one integer L (1<=L<=100), indicating the length of the fence.
The input ends with L=0.

## Output

For each test case, output one line containing the largest area. Your answer should be rounded to 2 digits after the decimal point.

## Sample Input

1
100
0

## Sample Output

0.16
1591.55

zhuweicong

## Source

2009 Shanghai Invitation Contest Host by DH