https://programmers.co.kr/learn/courses/30/lessons/12981
def solution(n, words):
answer = [0, 0]
history = set([words[0]])
for i in range(1, len(words)):
if words[i] in history or words[i-1][-1] != words[i][0]:
return [i%n+1, i//n+1]
history.add(words[i])
return answer