#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i = 0; i < (n);i++)
#define sz(x) int(x.size())
typedef long long ll;
typedef pair<int,int> P;
const int MAX = 510000;
const ll MOD = 1000000007;

long long fac[MAX], finv[MAX], inv[MAX];

// テーブルを作る前処理
void COMinit() {
    fac[0] = fac[1] = 1;
    finv[0] = finv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < MAX; i++){
        fac[i] = fac[i - 1] * i % MOD;
        inv[i] = MOD - inv[MOD%i] * (MOD / i) % MOD;
        finv[i] = finv[i - 1] * inv[i] % MOD;
    }
}

// 二項係数計算
long long COM(int n, int k){
    if (n < k) return 0;
    if (n < 0 || k < 0) return 0;
    return fac[n] * (finv[k] * finv[n - k] % MOD) % MOD;
}
ll mod_pow(ll x, ll n, ll mod = MOD){
    if(n == 0)return 1;
    ll res = mod_pow(x*x%mod,n/2,mod);
    if(n&1) res = res * x % mod;
    return res;
}
int main() {
  ll n, m;
  cin >> n >> m;
  COMinit();
  ll res = mod_pow(m, n);

  int cnt = 0;
  for (int x = m - 1; x >= 1; x--) {
    ll now = COM(m, x) * mod_pow(x, n) % MOD;
    if (cnt % 2 == 0) res = res - now + MOD;
    else res += now;
    cnt++;
    res %= MOD;
  }
  cout << res << endl;
  return 0; 
}