func_code_string: #include <bits/stdc++.h>   using namespace std;   long long s1[2100][2100], sum[2100][2100], cnt[2100][2100], cnt1[2100][2100];   int main() {     int n, m, i, j;     long long res;     scanf( %d%d , &n, &m);     for (i = 2; i <= m; i++) {       for (j = 1; j <= n; j++) {         cnt[i][j] = sum[i][j - 1] + 1;         cnt[i][j] %= 1000000007;         s1[i][j] = s1[i - 1][j] + cnt[i][j];         s1[i][j] %= 1000000007;         sum[i][j] = sum[i - 1][j] + s1[i][j];         sum[i][j] %= 1000000007;         cnt1[i][j] = cnt[i][j] - cnt[i][j - 1];         if (cnt1[i][j] < 0) cnt1[i][j] += 1000000007;       }     }     res = 0;     for (i = 2; i <= m; i++)       for (j = 1; j <= n; j++) {         res += ((cnt[i][j] * cnt1[i][n - j + 1]) % 1000000007) * (m - i + 1);         res %= 1000000007;       }     printf( %I64d n , res);     return 0;   }   