#include <bits/stdc++.h>
using namespace std;
const int maxn = 2010;
const int mod = 1000000007;
long long dp[maxn][maxn];
long long s[maxn][maxn], ss[maxn][maxn];
void upd(long long &t, long long k) {
  t += k;
  t %= mod;
}
int main() {
  int n, i, j, m;
  long long t;
  cin >> n >> m;
  for (i = 1; i <= n; i++) {
    for (j = 0; j + 1 < m; j++) {
      long long t = 1 + s[i - 1][j] * (j + 1) - ss[i - 1][j];
      upd(dp[i][j], t);
    }
    s[i][0] = dp[i][0];
    for (j = 1; j + 1 < m; j++) {
      s[i][j] = s[i][j - 1] + dp[i][j], ss[i][j] = ss[i][j - 1] + dp[i][j] * j;
      s[i][j] %= mod;
      ss[i][j] %= mod;
    }
  }
  long long ans = 0;
  for (i = 1; i <= n; i++) {
    for (j = 0; j + 1 < m; j++) {
      long long t1 = dp[i][j] - dp[i - 1][j];
      long long t2 = dp[n - i + 1][j];
      ans += t1 * t2 % mod * (m - j - 1);
      ans %= mod;
    }
  }
  cout << (ans + mod) % mod << endl;
}
