#include <bits/stdc++.h>
using namespace std;

constexpr int64_t mod = 1000000007;
vector<int64_t> fact, inv;

int64_t power(int64_t n, int64_t k) {
    if (k == 0) return 1;
    int64_t res = power(n * n % mod, k / 2);
    if (k % 2) res = res * n % mod;
    return res;
}

void init(int n) {
    fact.push_back(1);
    inv.push_back(1);
    for (int i = 1; i <= n; i++) {
        fact.push_back(fact.at(i - 1) * i % mod);
        inv.push_back(power(fact.at(i), mod - 2));
    }
}

int64_t ncr(int64_t n, int64_t r) {
    return fact.at(n) * inv.at(r) % mod * inv.at(n - r) % mod;
}

int main() {
    int n, m;
    cin >> n >> m;
    init(m);
    int64_t ans = 0, sign = 1;
    for (int i = 0; i < m; i++) {
        ans += sign * ncr(m, i) * power(m - i, n) + mod;
        ans %= mod;
        sign = -sign;
    }
    cout << ans << endl;
}