#include <bits/stdc++.h>

#define M_PI       3.14159265358979323846   // pi

using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef vector<ll> VI;
typedef pair<ll, ll> P;
typedef tuple<ll, ll, ll> t3;
typedef tuple<ll, ll, ll, ll> t4;
typedef tuple<ll, ll, ll, ll, ll> t5;

#define rep(a,n) for(ll a = 0;a < n;a++)
#define repi(a,b,n) for(ll a = b;a < n;a++)

using namespace std;

static const ll INF = 1e15;

const ll mod = 1000000007;

ll mpow(ll x, ll n) {
	ll ans = 1; x %= mod;
	while (n != 0) {
		if (n & 1) ans = ans * x % mod;
		x = x * x % mod;
		n = n >> 1;
	}
	return ans;
}

ll inv_mod(ll a) { return mpow(a, mod - 2); }

class Factorial {
private:
	vector<ll> fac;
	vector<ll> ifac;
public:

	Factorial(ll N) {
		fac.push_back(1);
		for (int i = 0; i < N; i++) fac.push_back(fac[i] * (i + 1) % mod);
		ifac.resize(N + 1);
		ifac[N] = inv_mod(fac[N]);
		for (int i = 0; i < N; i++) ifac[N - 1 - i] = (ifac[N - i] * (N - i)) % mod;
	}

	ll fact(ll a) { return fac[a]; }
	ll ifact(ll a) { return ifac[a]; }

	ll cmb(ll a, ll b) {
		if (a == 0 && b == 0) return 1;
		if (a < b || a < 0 || b < 0) return 0;
		ll tmp = ifact(a - b) * ifact(b) % mod;
		return tmp * fac[a] % mod;
	}
	ll per(ll a, ll b) {
		if (a == 0 && b == 0) return 1;
		if (a < b || a < 0 || b < 0) return 0;
		return fac[a] * ifac[a - b] % mod;
	}
};

int main() {
	ll n, m;
	cin >> n >> m;
	ll all = mpow(m, n);
	Factorial f(m);
	for (int i = 1; i < m; i++) {
		ll elem = f.cmb(m, i) * mpow(m - i, n);
		elem %= mod;
		ll sign = (i % 2 == 1) ? -1 : 1;
		all += sign * elem + mod;
		all %= mod;
	}
	cout << all << endl;
	return 0;
}