N = int(input())
M = int(input())
if M > N:
    print(0)
    exit()
S = [[0] * 20 for i in range(20)]
fact = [1] * 20
S[0][0] = 1
for n in range(1, 20):
    for k in range(0, 20):
        S[n][k] = S[n-1][k-1] + k * S[n-1][k]
    fact[n] = fact[n-1] * n
print(S[N][M]*fact[M])