func_code_string: #include <bits/stdc++.h>   #pragma comment(linker,  /stack:200000000 )   #pragma GCC optimize( O3 )   using namespace std;   const double eps = 1e-9;   const double pi = acos(-1.0);   const int inf = 2e5 + 10;   int mod = 1e9 + 7;   const int MAXN = 1e5 + 7;   long double C(int n, int k) {     long double res = 1.;     if (2 * k > n) k = n - k;     for (int i = 1; i <= k; ++i) {       res *= n - k + i;       res /= i;     }     return res;   }   int32_t main() {     ios_base::sync_with_stdio(0);     cout << fixed << setprecision(10);     cin.tie(0);     int n, m;     cin >> n >> m;     long double res = 0;     for (int k = 1; k <= min(n, m); ++k) {       res += C(m, k) * C(m * (n - 1), n - k) * k * k;     }     res /= n;     res /= C(n * m, n);     cout << res;     return 0;   }   