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.


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.


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




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rudra_hari007: 2020-09-27 14:54:18

What concept is needed for it?

shaon_debnath: 2020-09-16 20:03:49

Use M_PI present in <math.h> and printf("%.2f") for C++

avi_kumar15: 2020-05-23 23:43:58


elucidase: 2020-05-23 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: 2020-04-21 19:27:47

Use pi = 3.1415926536

devmayukh: 2019-11-24 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: 2019-08-12 13:58:05

Use pi = 3.14 got WA, use pi = 3.141592654 and AC.

dhia01: 2019-07-27 01:22:44


toolatetostart: 2019-06-17 13:03:22

@sarthak_1998 man don't mislead others due to u i got one wa,use pi=3.1415926536

abuhanif: 2019-05-25 19:50:35

Taking ur advice about PI=3.142 i got WA @sharthak_1998
Then used PI=2*acos(0.0) and AC

Added by:Fudan University Problem Setters
Time limit:1s
Source limit:50000B
Memory limit:1536MB
Cluster: Cube (Intel G860)
Languages:All except: C99 ERL JS-RHINO NODEJS PERL6 VB.NET
Resource:Fudan University Local Contest #1, practise session