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))