#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < n; i++)
using namespace std;

typedef long long ll;

ll mod_pow(ll x, ll n, ll mod) {
    ll res = 1;
    while (n > 0) {
        if (n & 1) res = res * x % mod;
        x = x * x % mod;
        n >>= 1;
    }
    return res;
}

int main() {
    ll MOD = 1e9 + 7;
    vector<ll> f(100001, 1);
    rep(i, 100000) f[i + 1] = (f[i] * (i + 1)) % MOD;
    ll N, M;
    cin >> N >> M;
    ll ans = mod_pow(M, N, MOD);
    for (int i = M - 1; i >= 1; i--) {
        ll d = mod_pow(i, N, MOD) * f[M];
        d %= MOD;
        d *= mod_pow(f[i], MOD - 2, MOD);
        d %= MOD;
        d *= mod_pow(f[M - i], MOD - 2, MOD);
        d %= MOD;
        if ((M - i) % 2) {
            ans = (ans - d + MOD) % MOD;
        } else {
            ans = (ans + d) % MOD;
        }
    }
    cout << ans << "\n";
}