from math import factorial

s = [[0] * 20 for _ in range(20)]
s[0][0] = 1
for i in range(20):
    for j in range(20):
        if i + 1 < 20:
            s[i + 1][j] += s[i][j]
        if j + 1 < 20:
            s[i][j + 1] += s[i][j] * i

n = int(input())
m = int(input())
if n == 0:
    print(int(m == 0))
else:
    print(s[m][n - m] * factorial(m) if m <= n else 0)