#include <bits/stdc++.h>
using namespace std;
const int maxn = 2 * 1000 + 3;
const long long MOD = 1000000007;
long long dp[maxn][maxn], sum[maxn][maxn];
long long memo(int i, int j) {
  if (i == 0) {
    dp[i][j] = 1ll;
    return 1ll;
  }
  if (j < 2) {
    dp[i][j] = 0ll;
    return 0ll;
  }
  if (i == 1) {
    dp[i][j] = (j * (j - 1) / 2) % MOD;
    return (j * (j - 1) / 2) % MOD;
  }
  if (dp[i][j] == -1)
    dp[i][j] =
        (memo(i - 1, j) + ((2 * memo(i, j - 1)) % MOD) - memo(i, j - 2)) % MOD;
  return dp[i][j];
}
int main() {
  memset(dp, -1, sizeof dp);
  int n, m;
  cin >> n >> m;
  memo(n, m);
  for (int i = 0; i <= n; i++)
    for (int j = 0; j <= m; j++)
      if (dp[i][j] == -1) dp[i][j]++;
  for (int i = 0; i <= m; i++) sum[0][i] = 1ll;
  for (int i = 1; i <= n; i++)
    for (int j = 0; j <= m; j++)
      sum[i][j] = (((sum[i][j] + sum[i - 1][j]) % MOD) + dp[i][j]) % MOD;
  long long ans = 0;
  for (int i = 1; i <= n; i++)
    for (int j = 2; j <= m; j++)
      ans =
          (ans + ((sum[i - 1][j] *
                   (((2 * sum[n - i][j - 1] - sum[n - i][j - 2]) + MOD) % MOD) %
                   MOD) *
                  (m - j + 1)) %
                     MOD) %
          MOD;
  cout << (ans + MOD) % MOD << endl;
  return 0;
}
