N, M = map(int, input().split())
MOD = 10 ** 9 + 7
modinv = lambda a, mod=MOD: pow(a, -1, mod)

if M > N:
    print(0)
    exit()

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