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#include <algorithm>
#include <iostream>
using namespace std;
const long long MOD = 1000000007;
const int MAXN = 3000;

#define FOR(i, n) for(int i = 0, __n = (n); i < __n; i++)

long long np[MAXN+1][MAXN+1];
long long p[MAXN+1][MAXN+1];

int main() {
  ios_base::sync_with_stdio(0);

  long long n, m; cin  >> n >> m;

  p[0][0] = 1;
  for (long long i = 1; i<=n; i++) {
    for (long long k = 1; k * 2-1<= n; k++) {
      p[i][k] = ((p[i-1][k] + np[i-1][k]) * k) % MOD;
      np[i][k] = (np[i-1][k] * (m-k) + p[i-1][k-1]) % MOD;
    }
  }
  // for (int i = 0; i<=n; i++) {
  //   cout << "p(" << i << "):";
  //   for (int k = 0; k<=n; k++) {
  //     cout << "\t" << p[i][k];
  //   }
  //   cout << "\tnp(" << i << "):";
  //   for (int k = 0; k*2-1<=n; k++) {
  //     cout << "\t" << np[i][k];
  //   }
  //   cout << endl;
  // }

  long long sum = 0;
  long long mult = 1;
  for (long long k = 1; k * 2 <= n; k++) {
    mult = (mult * (m - k + 1))%MOD;
    sum += mult * p[n][k];
    sum %= MOD;
  }

  cout << sum << endl;
}