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

n = 505050

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

def comb(n, r):
    if n < 0 or r < 0 or n - r < 0:
        return 0
    return fact[n] * invfact[r] * invfact[n - r] % mod

pm = 1
ans = 0
for i in range(M + 1):
    ans += comb(M, i) * pow(M - i, N, mod) * pm
    ans %= mod
    pm *= -1
print(ans)