완주하지 못한 선수 (해시, 딕셔너리)

from collections import Counter
def solution(participant, completion):

    dic1=Counter(participant)
    dic2=Counter(completion)

    answer=dic1-dic2
    return list(answer.keys())[0]

from collections import Counter
def solution(participant, completion):

    dic1=Counter(participant)
    dic2=Counter(completion)

    for x in dic1:
        if dic1[x]-dic2[x]!=0:
            return x