/* -*- coding: utf-8 -*-
 *
 * 1035.cc:  No.1035 Color Box - yukicoder
 */

#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<iostream>
#include<string>
#include<vector>
#include<map>
#include<set>
#include<stack>
#include<list>
#include<queue>
#include<deque>
#include<algorithm>
#include<numeric>
#include<utility>
#include<complex>
#include<functional>
 
using namespace std;

/* constant */

const int MAX_N = 100000;
const int MOD = 1000000007;

/* typedef */

typedef long long ll;

/* global variables */

int fs[MAX_N + 1], invfs[MAX_N + 1];

/* subroutines */

int powmod(int a, int n) {  // a^n % MOD
  int pm = 1;
  while (n > 0) {
    if (n & 1) pm = (ll)pm * a % MOD;
    a = (ll)a * a % MOD;
    n >>= 1;
  }
  return pm;
}

inline int nck(int n, int k) {  // nCk % MOD
  return (ll)fs[n] * invfs[n - k] % MOD * invfs[k] % MOD;
}

void prepare_fracs(int n) {
  fs[0] = invfs[0] = 1;
  for (int i = 1; i <= n; i++) {
    fs[i] = (ll)fs[i - 1] * i % MOD;
    invfs[i] = powmod(fs[i], MOD - 2);
  }
}

/* main */

int main() {
  int n, m;
  scanf("%d%d", &n, &m);

  prepare_fracs(n);

  int sum = 0;
  for (int i = 0; i < m; i++) {
    int d = (ll)powmod(m - i, n) * nck(m, m - i) % MOD;
    if (i & 1) d = MOD - d;
    sum = (sum + d) % MOD;
  }

  printf("%d\n", sum);
  return 0;
}