lightoj1022Circle in Square

 1 //Accepted    1088 KB    0 ms
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cmath>
 5 const double Pi=2*acos(0.0);
 6 double ans,r;
 7 double slove()
 8 {
 9     return 4*r*r-Pi*r*r;
10 }
11 int main()
12 {
13     int T;
14     scanf("%d",&T);
15     for (int t=1;t<=T;t++)
16     {
17         scanf("%lf",&r);
18         printf("Case %d: %.2f\n",t,slove()+1e-9);
19     }
20     return 0;
21 }