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


def modinv(a):
    return pow(a, MOD - 2, MOD)


temp_list = [1]
for i in range(0, (M // 2)):
    temp_list.append(int(((temp_list[-1] * ((M - i)) % MOD) * (modinv((i + 1))) % MOD)) % MOD)


before = 0
for i in range(1, M + 1):
    before = ((((temp_list[min([i, (M - i)])]) * pow(i, N, MOD)) % MOD) - before) % MOD

print(before % MOD)