#include "bits/stdc++.h"
#pragma warning(disable:4996)
using namespace std;
#define int long long
#define rep(i,n) for(int i=0;i<n;i++)
typedef pair<int, int> P;
const long long mod = 1000000007;
const long long inf = 1ll<<61;

int kj[200006], kji[200006];
int modpow(int a, int x) {
	int res = 1;
	while (x) {
		if (x & 1)res = res*a%mod;
		a = a*a%mod;
		x >>= 1;
	}
	return res;
}
void setkj() {
	kj[0] = 1;
	rep(i, 200005) {
		kj[i + 1] = kj[i] * (i + 1) % mod;
		kji[i] = modpow(kj[i], mod - 2);
	}
}
int comb(int n, int r) {
	return kj[n] * kji[r] % mod*kji[n - r] % mod;
}
signed main() {
	int n, m; cin >> n >> m;
	int ans = 0;
	setkj();
	for(int i=1;i<=m;i++) {
		if ((m - i) & 1)ans -= comb(m, i)*modpow(i, n) % mod;
		else ans += comb(m, i)*modpow(i, n) % mod;
		ans = (ans + mod) % mod;
	}
	cout << ans << endl;
}