#include <bits/stdc++.h>
#include <string>
#define ft first
#define sc second
#define pt(sth) cout << sth << "\n"
#define chmax(a, b) (a)=max(a, b)
#define chmin(a, b) (a)=min(a, b)
#define moC(a, s, b) (a)=((a)s(b)+MOD)%MOD
using namespace std;
typedef long long ll;
typedef pair<ll, ll> pll;
static const ll INF=1e18;
static const ll MAX=101010;
static const ll MOD=1e9+7;

/*
 for(i=0; i<N; i++)
   cin >> a[i];
*/
 
ll moP(ll x, ll n) {
  ll res=1;
  while(n>0) {
    if(n&1) moC(res, *, x);
    moC(x, *, x);
    n>>=1;
  }
  return res;
}

ll fa[MAX], rf[MAX];

ll C(ll n, ll k) {
  if(n<k||n<0||k<0) return 0;
  if(k==0) return 1;
  if(n==k) return 1;
  return fa[n]*rf[k]%MOD*rf[n-k]%MOD;
}

ll N, M;
ll f(ll i) {
  if(i==0) return 0;
  return (C(M, i)*moP(i, N)%MOD-f(i-1)%MOD+MOD)%MOD;
}

int main(void) {
  ll i, j, k;
  
  cin >> N >> M;
  
  fa[0]=rf[0]=1;
  for(i=1; i<MAX; i++) {
    fa[i]=fa[i-1]*i%MOD;
    rf[i]=moP(fa[i], MOD-2);
  }
  
  pt(f(M));
  
}