SPOJ : FENCE1 Solution

#include<cstdio>
#include<cstring>
#include<algorithm>
#include<queue>
#include<iostream>
#define LL long long
using namespace std;

int main()
{
   int a;//Don't use 22/7 or 22.0/7.0 because its value is different    double pi=3.14159265359;
   while(scanf("%d",&a) && a!=0)
   {
      printf("%.2lf\n",(double)(a*a)/pi/2);
  }

   return 0;
}