1062.py

from sys import stdin, exit

def dfs(idx, cnt):
    global answer

    if cnt == k - 5:
        read_cnt = 0
        for word in words:
            for w in word:
                if not learn[ord(w) - ord('a')]:
                    break
            else:
                read_cnt += 1
        answer = max(answer, read_cnt) if answer else read_cnt
        return

    for i in range(idx, 26):
        if not learn[i]:
            learn[i] = True
            dfs(i, cnt + 1)
            learn[i] = False


answer = 0
n, k = map(int, stdin.readline().split())

if k < 5 or k == 26:
    print(0 if k < 5 else n)
    exit(0)

words = [set(stdin.readline().rstrip()) for _ in range(n)]
learn = [False] * 26

for c in ('a', 'c', 'i', 'n', 't'):
    learn[ord(c) - ord('a')] = True

dfs(0, 0)
print(answer)