N, M = map(int, input().split())
MOD = 10 ** 9 + 7
fact = [1] * (M + 1)
rfact = [1] * (M + 1)
r = 1
for i in range(1, M + 1):
    fact[i] = r = r * i % MOD
rfact[M] = r = pow(fact[M], -1, MOD)
for i in range(M, 0, -1):
    rfact[i - 1] = r = r * i % MOD

# nCk (mod MOD) を求める
def comb(n, k):
    return fact[n] * rfact[k] * rfact[n - k] % MOD

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