#include<iostream>
using namespace std;
const int MOD = 1000000007;
const int MAX_M = 100005;


long long mypow(long long p, long long n) {
    if (n == 0) return 1;
    long long t = mypow(p, n / 2);
    return n % 2 == 0 ? t * t % MOD : t * t % MOD * p % MOD;
}

long long myadd(long long a, long long b) {
    return (a + b) % MOD;
}

long long mysub(long long a, long long b) {
    return (MOD + a - b) % MOD;
}

long long mymul(long long a, long long b) {
    return a * b % MOD;
}

long long mydiv(long long a, long long b) {
    return a * mypow(b, MOD - 2) % MOD;
}

int factorial[MAX_M];
void calcFactorial() {
    factorial[0] = 1;
    for (int i = 1; i < MAX_M; ++i) {
        factorial[i] = mymul(factorial[i - 1], i);
    }
}

long long nCk(long long n, long long k) {
    return mydiv(factorial[n], mymul(factorial[k],factorial[n - k]));
}


long long N, M;

void read() {
    cin >> N >> M;
}


void work() {
    long long ans = 0;

    ans = myadd(ans, mypow(M, N));
    
    for (int k = 1; k < M; ++k) {
        if (k % 2 == 0) {
            ans = myadd(ans, mymul(nCk(M, k), mypow(M - k, N)));
        }
        else {
            ans = mysub(ans, mymul(nCk(M, k), mypow(M - k, N)));
        }
    }

    cout << ans << endl;
}


int main() {
    calcFactorial();
    read();
    work();
    return 0;
}