FENCE1  Build a Fence
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.
Example
Input: 1 0 Output: 0.16
hide comments
darkdeveloper:
20210801 18:35:04
Use pi = 3.1415926536


loser_404:
20210607 16:41:51
for clear concept:


yasser1110:
20210523 18:22:08
Make sure you use "fixed", if you use cout (like: cout<<fixed<<setprecision(2)<<ans<<endl;), in cpp otherwise you print results in the exponential format (like 1.6e+03, for 100). Or just use printf. 

rudra_hari007:
20200927 14:54:18
What concept is needed for it?


shaon_debnath:
20200916 20:03:49
Use M_PI present in <math.h> and printf("%.2f") for C++ 

avi_kumar15:
20200523 23:43:58
cout<<fixed<<setprecision(2)<<ans<<endl; 

elucidase:
20200523 08:02:58
Since at the optimum we should observe symmetry (otherwise strictly worse), we can reflect the fence across the wall. The problem is then equivalent to finding the maximum area of the closed shape given its parameter. 

sheersha:
20200421 19:27:47
Use pi = 3.1415926536 

devmayukh:
20191124 10:44:49
Why are you defining Pi yourself? There is M_PI in <math.h> in C/C++, and Math.PI in Java. 

quannguyenlhp:
20190812 13:58:05
Use pi = 3.14 got WA, use pi = 3.141592654 and AC. 
Added by:  Fudan University Problem Setters 
Date:  20090523 
Time limit:  1s 
Source limit:  50000B 
Memory limit:  1536MB 
Cluster:  Cube (Intel G860) 
Languages:  All except: C99 ERL JSRHINO NODEJS PERL6 VB.NET 
Resource:  Fudan University Local Contest #1, practise session 