중복 없는 순열
from itertools import permutations
중복 없는 조합
from itertools import combinations
중복 있는 순열 / 각 집단에서 추출
from itertools import product
중복 있는 조합
from itertools import combinations_with_replacement as com
from itertools import permutations
from itertools import combinations
from itertools import product
from itertools import combinations_with_replacement as com
