완주하지 못한 선수

# 처음 낸 답
def solution(participant, completion):
    participant.sort()
    completion.sort()
    for p, c in zip(participant, completion):
        if p != c:
            return p
    return participant[-1]

# 이런 것도 있었다..!
import collections


def solution(participant, completion):
    answer = collections.Counter(participant) - collections.Counter(completion)
    return list(answer.keys())[0]