题解 | #牛牛的排列数#
牛牛的排列数
http://www.nowcoder.com/practice/9ca1c236cdbf46da9e08e1f510808625
def compute_x(num):
if num<=0:
return 0
elif num==1:
return 1
else:
return num*compute_x(num-1)
n,m=list(map(int,input().split()))
a=compute_x(n)
b=compute_x(n-m)
if b==0:
print(0)
else:
print(int(a/b))
