class Ncrs():
    def __init__(self, max_r, mod = 10**9+7) -> None:
        self.mod = mod
        self.fct, self.inv = [1] * (max_r+2), [1]* (max_r+2)
        for i in range(2, max_r+1):
            self.fct[i] = self.fct[i-1] * i % mod
            self.inv[max_r] = pow(self.fct[max_r], mod-2, mod)
        for i in range(max_r, 0,-1):
            self.inv[i-1] = self.inv[i] * i % mod
    def __call__(self, n, k) -> int:
        return self.nck(n, k)
    def nck(self, n, k) -> int:
        if k > n or n <0 or k <0:
            return 0
        return self.fct[n] * self.inv[k] % self.mod * self.inv[n-k] % self.mod

N, M = map(int, input().split())
res, w = 0, 1
mod = 10**9+7
ncr = Ncrs(M)
for i in range(M, 0, -1):
    res += (w*ncr(M,i)*pow(i, N, mod))%mod
    res %= mod
    w *= -1
print(res)