#include <cstdio>

using namespace std;

typedef long long ll;

const ll mod = 1e9+7;

ll modpow(ll a, ll b) {
  if (b == 0) return 1;
  ll ret = modpow(a*a%mod, b/2);
  if (b%2 == 1) ret = (ret*a)%mod;
  return ret;
}

/*
ll C(ll n, ll k) {
  ll p = 1, q = 1;
  for (int i = n; i >= 1; i--) p = (p*i)%mod;
  for (int i = k; i >= 1; i--) q = (q*i)%mod;
  for (int i = n-k; i >= 1; i--) q = (q*i)%mod;
  return (p * modpow(q, mod-2))%mod;
}
*/

int main(void) {
  ll n, m;
  scanf("%lld%lld", &n, &m);
  // printf("%lld\n", modpow(m, n) - (modpow(2, n)-1)*m);
  ll res = 0;
  int sig = modpow(-1, m-1);
  ll p = 1, q = 1;
  
  for (int i = 1; i <= m; i++) {
    p = (p*i)%mod;
  }
  for (int i = 1; i <= m-1; i++) {
    q = (q*i)%mod;
  }
  
  for (int i = 1; i <= m; i++) {
    ll C = (p*modpow(q, mod-2))%mod;
    // res = ((res+(C(m, i) * modpow(i, n)%mod*sig))%mod+mod)%mod;
    res = ((res+(C * modpow(i, n)%mod*sig))%mod+mod)%mod;
    sig = -sig;
    q = (q * (i+1))%mod;
    q = (q * modpow(m-i, mod-2))%mod;
    // printf("%lld\n", res);
  }
  printf("%lld\n", res);
}