func_code_string: #include <bits/stdc++.h>   using namespace std;   long long f[2010][2010], n, s, ans, m;   int main() {     int n, m;     cin >> n >> m;     for (int i = 1; i <= n; ++i) {       s = 0;       for (int j = 0; j <= m - 2; ++j)         s = (s + f[i - 1][j]) % 1000000007,         f[i][j] = ((j == 0 ? 1 : f[i][j - 1]) + s) % 1000000007;     }     for (int i = 1; i <= n; ++i)       for (int j = 0; j <= m - 2; ++j)         ans = (ans + (m - j - 1) * (f[i][j] - f[i - 1][j]) % 1000000007 *                          f[n - i + 1][j] % 1000000007) %               1000000007;     cout << (ans + 1000000007) % 1000000007;   }   