#include <iostream>
#include <vector>

using namespace std;
using ll = long long;
const ll MOD = (ll)1e9 + 7;

//Combination Mod
class Combination_Mod {
public:
	vector<long long> fac, finv, inv;
	long long MOD;

	Combination_Mod(int N, long long mod) : fac(vector<long long>(N + 1)), finv(vector<long long>(N + 1)), inv(vector<long long>(N + 1)), MOD(mod) {
		fac[0] = fac[1] = finv[0] = finv[1] = inv[1] = 1;
		for (int i = 2; i <= N; ++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;
		}
	}

	long long num(int n, int k) {
		return ((n < 0 || k < 0 || n < k) ? 0 : fac[n] * (finv[k] * finv[n - k] % MOD) % MOD);
	}
};

//Pow_Mod O(log(n))
long long Pow_Mod(long long x, long long n, long long mod) {
	long long res = 1;
	for (; n > 0; n >>= 1, (x *= x) %= mod) if (n & 1) (res *= x) %= mod;
	return res;
}

int main() {
	ll N, M, ans = 0, sgn = 1; cin >> N >> M;
	Combination_Mod CM(M, MOD);
	for (ll i = M; 1 <= i; --i) {
		(ans += (MOD + sgn*((CM.num(M, i)*Pow_Mod(i, N, MOD)))) % MOD) %= MOD;
		sgn *= -1;
	}
	cout << ans << endl;

	return 0;
}