#include <bits/stdc++.h>
#include <atcoder/all>
using mint = atcoder::modint1000000007;
using namespace std;

int main() {
	int n, m;
	cin >> n >> m;
	vector<mint> fact = {1};
	for (int i = 1; i < 1010101; i++){
		fact.push_back(fact.back() * (mint)i);
	}
	auto cmb = [&](int n,int r){
		return fact[n] / fact[n - r] / fact[r];
	};
	vector<mint> f(n + 1);
	for (int i = 1; i <= m; i++){
		f[i] = cmb(m, i) * (mint(i)).pow(n) - f[i - 1];
	}
	cout << f[m].val() << endl;
}