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

def comb(n, k):
    return fact[n] * rfact[k] * rfact[n - k] % MOD

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