콜라츠 추측

def solution(num):
    count = 0
    if num == 1:
        pass
    else:
        while num != 1:
            if count < 500: 
                if num % 2 == 0:
                    num = num / 2
                    count = count + 1
                else:
                    num = num * 3 + 1
                    count = count + 1
            else:
                count = -1
                break
    return count