#include <bits/stdc++.h>
using namespace std;
int f[2005][2005] = {0};
int g[2005][2005] = {0};
int h[2005][2005] = {0};
int k[2005][2005] = {0};
int n, m;
int main() {
  int ans = 0;
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= n; i++) {
    for (int l = 2; l <= m; l++) {
      k[i][l] = f[i][l] =
          (1ll * (l + 1) * f[i - 1][l] - g[i - 1][l] + 1) % 1000000007;
      h[i][l] =
          (1ll * (l + 1) * f[i - 1][l - 1] - g[i - 1][l - 1] + 1) % 1000000007;
    }
    for (int l = 2; l <= m; l++) {
      g[i][l] = (g[i][l - 1] + 1ll * l * f[i][l]) % 1000000007;
      f[i][l] = (f[i][l - 1] + f[i][l]) % 1000000007;
    }
  }
  for (int i = 1; i <= n; i++)
    for (int l = 2; l <= m; l++) {
      ans = (ans + 1ll * (m - l + 1) *
                       (1ll * k[i][l] * h[n - i + 1][l] % 1000000007)) %
            1000000007;
    }
  printf("%d\n", (ans + 1000000007) % 1000000007);
  return 0;
}
