#include <bits/stdc++.h>
using namespace std;
const int MAXN = 2000 + 10;
const int mod = 1000000007;
int n, m;
int dp[MAXN][MAXN], func[MAXN][MAXN], C[MAXN][MAXN], f0[MAXN][MAXN],
    f1[MAXN][MAXN], sum[MAXN][MAXN];
int main() {
  for (int i = 0; i < MAXN; i++) {
    C[i][0] = 1;
    for (int j = 1; j <= i; j++)
      C[i][j] = (C[i - 1][j] + C[i - 1][j - 1]) % mod;
  }
  cin >> n >> m;
  for (int i = 2; i <= m; i++) {
    dp[1][i] = 1;
    func[1][i] = (func[1][i - 1] + (1 - i)) % mod;
    sum[1][i] = sum[1][i - 1] + 1;
  }
  for (int i = 2; i <= n; i++) {
    for (int j = 2; j <= m; j++) {
      dp[i][j] = ((long long)sum[i - 1][j] * j + func[i - 1][j]) % mod;
      sum[i][j] = (sum[i][j - 1] + dp[i][j]) % mod;
      func[i][j] = (func[i][j - 1] + (long long)(1 - j) * dp[i][j]) % mod;
    }
  }
  for (int j = 2; j <= m; j++)
    for (int i = 1; i <= n; i++) {
      f0[j][i] =
          ((long long)f0[j][i - 1] + (long long)dp[i][j] - dp[i - 1][j]) % mod;
      f1[j][i] = ((long long)f1[j][i - 1] + dp[i][j]) % mod;
    }
  int ret = 0;
  for (int i = 1; i <= n; i++)
    for (int j = 2; j <= m; j++)
      ret = (ret + (long long)(m - j + 1) * (long long)f0[j][i] % mod *
                       f1[j][n - i + 1] % mod) %
            mod;
  ret %= mod;
  ret += mod;
  ret %= mod;
  cout << ret << endl;
  return 0;
}
