func_code_string: #include <bits/stdc++.h>   using namespace std;   const long long N = 2e5 + 5, M = 1e18 + 5, OO = 0x3f3f3f3f;   const double pi = 3.141592653589793238462643383279502884;   double n, r;   double calc() {     double ang = 180 / n;     ang = (ang / 180) * pi;     double a = (sin(ang / 2) * r) / sin(pi - (1.5 * ang));     double ans = n * a * r * sin(ang);     return ans;   }   int main() {     cin >> n >> r;     printf( %.12lf  n , calc());     return 0;   }   