func_code_string: #include <bits/stdc++.h>   using namespace std;   const double PI = 3.1415926535;   double cot(double x) { return cos(x) / sin(x); }   int main() {     double r, n;     cin >> n >> r;     cout << fixed << setprecision(9)          << n * r * r * sin(PI / n) / (1 + 2 * cos(PI / n));     return 0;   }   