#include <bits/stdc++.h>
const int mod = 1000000007;
const int N = 2000 + 5, M = 2000 + 5;
int n, m;
long long f[N][M], np_f[N][M], np_fm[N][M], pn_f[N][M], pp_f[N][M], pp_fm[N][M];
int main() {
  scanf("%d%d", &n, &m);
  for (int i = 1; i <= n; ++i) {
    if (i == 1)
      for (int j = 2; j <= m; ++j) f[i][j] = 1;
    else
      for (int j = 2; j <= m; ++j)
        f[i][j] = (np_f[i - 1][j] * (j + 1) - np_fm[i - 1][j] + mod) % mod;
    for (int j = 1; j <= m; ++j) {
      np_fm[i][j] = (np_fm[i][j - 1] + f[i][j] * j) % mod;
      np_f[i][j] = (np_f[i][j - 1] + f[i][j]) % mod;
      pn_f[i][j] = (pn_f[i - 1][j] + f[i][j]) % mod;
    }
  }
  for (int i = 1; i <= n; ++i)
    for (int j = 1; j <= m; ++j) {
      pp_f[i][j] = (pp_f[i - 1][j] + np_f[i][j]) % mod;
      pp_fm[i][j] = (pp_fm[i - 1][j] + np_fm[i][j]) % mod;
    }
  long long ans = 0;
  for (int k = 1; k <= n; ++k)
    for (int j = 2; j <= m; ++j) {
      ans =
          (ans +
           (m - j + 1) * pn_f[k][j] % mod *
               ((1 + pp_f[n - k][j - 1] * (j + 1) - pp_fm[n - k][j - 1] + mod) %
                mod)) %
          mod;
    }
  printf("%I64d\n", ans);
  return 0;
}
