n, m = map(int, input().split())
if n < m:
    print('0')
else:
    shang = 1
    xia = 1
    cha = n - m
    for i in range(1,n+1):
        shang = shang * i
    for i in range(1,cha+1):
        xia = xia * i
    A = shang // xia
    print(int(A))