m=int(input())
n=int(input())
t=m-n
x=1
for i in range(1,m+1):
x=x*i
y=1
for j in range(1,n+1):
y=y*j
z=1
for k in range(1,t+1):
z=z*k
C=(x-y)/z
print(C)

def jc(x):
if x==1:
return 1
return x*jc(x-1)
m=int(input())
n=int(input())
c=(jc(m)-jc(n))/jc(m-n)
print(c)