MOD = 10**9+7
n, m = map(int, input().split())

U = m
fact = [0]*(U+1)
fact[0] = 1
for i in range(1, U+1):
    fact[i] = fact[i-1]*i % MOD


invfact = [0]*(U+1)
invfact[U] = pow(fact[U], MOD-2, MOD)
for i in reversed(range(U)):
    invfact[i] = invfact[i+1]*(i+1) % MOD


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


ans = 0
for i in range(m):
    if i % 2 == 0:
        ans += pow(m-i, n, MOD)*nCr(m, i)
    else:
        ans -= pow(m-i, n, MOD)*nCr(m, i)
    ans %= MOD
print(ans)