func_code_string: #include <bits/stdc++.h>   using namespace std;   double n, r;   signed main() {     scanf( %lf%lf , &n, &r);     printf( %.10f n , 2.0 * n * 0.5 * r * r * sin(acos(-1.0) / (2.0 * n)) /                           sin(acos(-1.0) - (acos(-1.0) / (2.0 * n)) * 3) *                           sin(2 * acos(-1.0) / (2.0 * n)));     return 0;   }   