class ModComb:
    def __init__(self, n: int, mod: int):
        fact = [0] * (n+1)
        fact[0] = 1
        for i in range(1, n+1):
            fact[i] = i * fact[i-1] % mod

        ifact = [0] * (n+1)
        ifact[n] = pow(fact[n], mod-2, mod)
        for i in range(n, 0, -1):
            ifact[i-1] = ifact[i] * i % mod
        self.fact = fact
        self.ifact = ifact
        self.mod = mod

    def __call__(self, n: int, k: int) -> int:
        if n < 0 or k > n: return 0
        return (self.fact[n] * self.ifact[k] % self.mod) * self.ifact[n-k] % self.mod


MOD = 10**9 + 7
N, M = map(int, input().split())

mcomb = ModComb(M, MOD)
ans = 0
for k in range(M+1):
    sgn = 1 if k % 2 == 0 else -1
    ans += sgn * mcomb(M, k) * pow(M-k, N, MOD)
    ans %= MOD

print(ans)