백준 11050번(python)

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N, K = list(map(int, input().split()))

up = 1
for i in range(N, N-K, -1):
    up *= i

down = 1
for i in range(1, K+1):
    down *= i

print(up // down)

math.factorial 활용

from math import factorial

N, K = list(map(int, input().split()))

print(factorial(N)//(factorial(K) * factorial(N-K)))