#include <bits/stdc++.h>
#define rep(i,n) for(int i=0;i<n;i++)
using namespace std;
using ll =  long long ;
using P = pair<int,int> ;
const int INF = 1e9;
const int MOD = 1000000007;


const int MAX = 1000000;
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;
}

long long modpow(long long a, long long b){
        bitset<40> bit(b);
        string s = bit.to_string();
        long long ret = 1;
        for (int i = 0;i< s.length(); ++i){
                ret = (ret * ret) % MOD;
                if(s[i]-'0') ret = (ret * a) % MOD;
        }
        return ret;
}

int main(){
    COMinit();
    int n,m;
    cin >> n >> m;
    ll ans = 0;
    ans += modpow(m,n);
    int plus = -1;
    for(int i=m-1;i>=1;i--){
        ll res = (plus * COM(m,i) * modpow(i,n))%MOD;
        ans = (ans + res + MOD)%MOD;
        plus *= -1;
    }
    cout << ans << endl;
    return 0;
}