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#include <bits/stdc++.h>
using namespace std;

const int MOD = 1e9 + 7;

int main() {
  int n, m;
  cin >> n >> m;

  vector<int> dp(2);
  dp[2 * 0 + 0] = 0;
  dp[2 * 0 + 1] = 1;

  for (int l = 1; l <= n; ++l) {
    vector<int> next(dp.size() + 2);
    for (int i = 0; i < dp.size() / 2; ++i) {
      next[2 * i + 1] = ((dp[2 * i + 0] + dp[2 * i + 1]) * (int64_t)i) % MOD;
      next[2 * i + 0] = (next[2 * i + 0] + dp[2 * i + 0] * (int64_t)(m - i)) % MOD;
      next[2 * (i + 1) + 0] = (dp[2 * i + 1] * (int64_t)(m - i)) % MOD;
    }
    dp = next;
  }

  int64_t result = 0;
  for (int i = 0; i < dp.size() / 2; ++i)
    result += dp[2 * i + 1];
  result %= MOD;

  cout << result << endl;
}