def solution(participant, completion):
    find_val, find_val2 = {},{}

    for j,i  in zip(participant,completion):
        count = find_val.get(j,0)
        find_val[j] = count + 1
        count = find_val2.get(i,0)
        find_val2[i] = count + 1
    
    for key in find_val:
        try:
            if find_val[key] != find_val2[key]:
                answer = key
        except KeyError:
            answer = key
    return answer