프로그래머스 12981 Python [영어 끝말잇기]

def solution(n, words):
    used = {words[0]}
    for i in range(1, len(words)):
        if words[i][0] != words[i - 1][-1] or words[i] in used:
            return [(i % n) + 1, (i // n) + 1]
        used.add(words[i])
    return [0, 0]