//#include <bits/stdc++.h>
#include <iostream>
#include <fstream>
#include <vector>
#include <string>
#include <cmath>
#include <algorithm>
#include <map>
#include <iomanip>
#include <stdlib.h>
#include <stdio.h>
#include <queue>
#include <deque>
#include <set>
#include <stack>
#include <time.h>
 
using namespace std;
 
typedef long long ll;
typedef long double ld;
typedef pair<int, int> Pii;
typedef pair<int, ll> Pil;
typedef pair<ll, ll> Pll;
typedef pair<ll, int> Pli;

#define fi first
#define se second
#define mp make_pair
 
const ll MOD = 1e9 + 7;
const ll MOD2 = 998244353;
const ll INF = 1ll << 60;
const double PI = 2 * asin(1);

void yes() {printf("yes\n");}
void no() {printf("no\n");}
void Yes() {printf("Yes\n");}
void No() {printf("No\n");}
void YES() {printf("YES\n");}
void NO() {printf("NO\n");}

ll Pow(ll A, ll N){
  if (N == 0) return 1;
  if (N % 2 == 0) return Pow(A * A % MOD, N / 2) % MOD;
  else return A * Pow(A * A % MOD, N / 2) % MOD;
}

ll N, M;
ll P[100005], nCr[100005];

int main(){
  cin >> N >> M;
  for (int i = 0; i < M; i++){
    P[i] = Pow(M - i, N);
  }

  nCr[0] = 1;
  for (ll i = 1; i < M; i++){
    nCr[i] = nCr[i - 1] * (M - i + 1); nCr[i] %= MOD;
    nCr[i] *= Pow(i, MOD - 2); nCr[i] %= MOD;
  }

  ll ans = 0;
  for (int i = 0; i < N; i++){
    if (i % 2 == 0) ans += P[i] * nCr[i];
    else ans -= P[i] * nCr[i];
    ans %= MOD;
    if (ans < 0) ans += MOD;
  }
  cout << ans << endl;


  return 0;
}