func_code_string: #include <bits/stdc++.h>   using namespace std;   static const int INF = 500000000;   template <class T>   void debug(T a, T b) {     for (; a != b; ++a) cerr << *a <<    ;     cerr << endl;   }   int n, w, b;   const long long int mod = 1000000009;   int C[4005][4005];   int main() {     for (int i = 0; i < 4003; ++i) {       C[i][0] = 1;       for (int j = 0; j < i; ++j)         C[i][j + 1] = (C[i - 1][j + 1] + C[i - 1][j]) % mod;     }     cin >> n >> w >> b;     long long int res = 0;     for (int l = 1; l < n - 1; ++l)       for (int r = l + 1; r < n; ++r) {         int len = r - l, wlen = n - len;         if (b - len < 0 || w - wlen < 0) continue;         res += C[b - 1][b - len] * (long long int)C[w - 1][w - wlen] % mod;         res %= mod;       }     for (int i = 0; i < w; ++i) res = res * (i + 1) % mod;     for (int i = 0; i < b; ++i) res = res * (i + 1) % mod;     cout << res << endl;     return 0;   }   