#define _GLIBCXX_DEBUG
#include "bits/stdc++.h"
//#include <intrin.h>  //AtCoder (gcc) 上ではこれがあると動かない。__popcnt用のincludeファイル。
using namespace std;
using Graph = vector<vector<int>>;

typedef long long ll;
typedef long double ld;


#define int long long
#define rep(i, n) for(long long i = 0; i < (n); i++)
#define sqrt(d) pow((long double) (d), 0.50)

const int INF = 2e9;
const ll large_P = 1e9 + 7;



//繰り返し2乗法
//N^aの、Mで割った余りを求める。
ll my_pow(ll N, ll a, ll M) {
	ll tempo;
	if (a == 0) {
		return 1;
	}
	else {
		if (a % 2 == 0) {
			tempo = my_pow(N, a / 2, M);
			return (tempo * tempo) % M;
		}
		else {
			tempo = my_pow(N, a - 1, M);
			return (tempo * N) % M;
		}
	}
}



//N_C_a を M で割った余り
ll my_combination(ll N, ll a, ll M) {
	ll answer = 1;

	rep(i, a) {
		answer *= (N - i);
		answer %= M;
	}

	rep(i, a) {
		answer *= my_pow(i + 1, M - 2, M);
		answer %= M;
	}

	return answer;
}



signed main() {
	int N, M;
	cin >> N >> M;

	ll res = 0LL;

	vector<ll> combination(M + 1, 0);  //i番目に M_C_i

	for (int i = M; i >= 1; i--) {
		if (i == M) {
			combination.at(M - i) = 1;
		}
		else {
			combination.at(M - i) = combination.at(M - i - 1) * (i + 1);
			combination.at(M - i) %= large_P;
			
			combination.at(M - i) *= my_pow(M - i, large_P - 2, large_P);
			combination.at(M - i) %= large_P;
		}
		ll temp = (my_pow(i, N, large_P) * combination.at(M - i)) % large_P;


		if ((M - i) % 2 == 0) {
			res += temp;
			res %= large_P;
			//cout << res << endl;
		}
		else {
			res -= temp;
			res %= large_P;
			//cout << res << endl;
		}
	}

	if (res < 0) res += large_P;

	cout << res << endl;
		
	//rep(i, M+1) {
		//cout << i << ": " << combination.at(i) << endl;;
	//}

	//cout << -576992686 + large_P << endl;
}