https://www.acmicpc.net/problem/11050
#풀이 1
import math
n,k = map(int, input().split())
result= math.factorial(n) // (math.factorial(k) * math.factorial(n-k))
print(result)
#풀이 2
n,k = map(int, input().split())
if k > n//2:
k = n-k
temp1 = 1
temp2 = 1
for i in range(n,n-k,-1):
temp1 *= i
for i in range(k,0,-1):
temp2 *= i
print(temp1//temp2)