func_code_string: #include <bits/stdc++.h>   using namespace std;   using ll = long long;   const long double PI2 = atan2(1.L, 0.L);   int main() {     ios_base::sync_with_stdio(0);     cin.tie(0);     int n;     long double r;     cin >> n >> r;     long double res =         r * r * n * sin(PI2 / n) * sin(2 * PI2 / n) / sin(3 * PI2 / n);     cout << fixed << setprecision(10) << res <<   n ;   }   