while True:
a,b = map(int,input().split())
if a== b == 0:
break
k = 1
if b >= a-b:
k1 = b
k2 = a-b
else:
k1 = a-b
k2 = b
for i in range(k1+1,a+1):
k*=i
for i in range(2,k2+1):
k//=i
print(k)