#include <iostream>
#include <vector>
#include <map>

using namespace std;
constexpr long long MOD = 1000000007;

//Combination Mod
class CombinationMod {
public:
	vector<long long> fac,finv,inv;
	long long mod;

	CombinationMod(int N,long long mod) : fac(N + 1), finv(N + 1), inv(N + 1), mod(mod) {
		fac[0] = fac[1] = finv[0] = finv[1] = inv[1] = 1;
		for (int i = 2; i <= N; ++i) {
			fac[i] = fac[i - 1] * i % mod;
			inv[i] = mod - inv[mod%i] * (mod / i) % mod;
			finv[i] = finv[i - 1] * inv[i] % mod;
		}
	}
	
	long long num(int n, int k) {
		return ((n < 0 || k < 0 || n < k) ? 0 : fac[n] * (finv[k] * finv[n - k] % mod) % mod);
	}
};

//Pow_Mod O(log(n))
long long PowMod(long long x, long long n, long long mod) {
    long long res = 1;
    for (; n > 0; n >>= 1, (x *= x) %= mod) if (n & 1) (res *= x) %= mod;
    return res;
}

int main(void) {
    int N,M; cin >> N >> M;
    CombinationMod CM(M,MOD);
    int sgn = 1;
    long long ans = 0;
    for(int i = M; 1 <= i; --i) {
        long long cnt = (sgn+MOD) % MOD;
        (cnt *= CM.num(M,i)) %= MOD;
        (cnt *= PowMod(i,N,MOD)) %= MOD;
        (ans += cnt) %= MOD;
        sgn *= -1;
    }
    cout << ans << endl;

    return 0;
}