#include <bits/stdc++.h>
using namespace std;

#define int long long
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }

#define MOD 1000000007

template<int64_t mod> struct Combination{
    vector<int64_t> f, rf;
 
    Combination(int max_n): f(max_n+1), rf(max_n+1){
        f[0] = 1;
        for(int i = 1;i <= max_n;i++) f[i] = f[i-1] * i % mod;
		int64_t a = f[max_n], inv = 1;
		for(int64_t b = mod-2;b > 0;b>>=1){
			if(b & 1) inv = inv*a % mod;
			a = a * a % mod;
		}
		for(int i = max_n;i >= 0;i--) inv = (rf[i] = inv) * i % MOD;
    }
 
    int64_t operator()(int n, int r){
        return (r < 0 || n < r) ? 0 : f[n] * rf[r] % mod * rf[n-r] % mod;
    }
};

int pow_mod(int n, int m){
	int ans = 1;
	while(m > 0){
		if(m & 1) ans = (ans * n) % MOD;
		n = (n * n) % MOD;
		m >>= 1;
	}
	return ans;
}

signed main(){
	int n, m;
	cin >> n >> m;
	Combination<MOD> ncr(m);

	bool f = true;
	int ans = 0;
	for(int i = m;i >= 1;i--){
		int tmp = pow_mod(i, n) * ncr(m, i) % MOD;
		if(f){
			ans = (ans + tmp) % MOD;
		}else{
			ans = (MOD+ans-tmp) % MOD;
		}
		f = !f;
	}

	cout << ans << endl;

	return 0;
}