#include <atcoder/all>
using namespace std;
using mint = atcoder::modint1000000007;

int main(){
	int n, m;
	cin >> n >> m;
	
	vector<mint> fact(m + 1), inv(m + 1);
	fact[0] = 1;
	for(int i = 1; i <= m; i++) fact[i] = i * fact[i - 1];
	inv[m] = 1 / fact[m];
	for(int i = m; i >= 1; i--) inv[i - 1] = i * inv[i];
	
	mint ans;
	for(int i = 1; i <= m; i++){
		ans += (m - i & 1 ? -1 : 1) * inv[m - i] * inv[i] * mint(i).pow(n);
	}
	
	cout << (ans * fact[m]).val() << '\n';
}