while True:
    score = input("输入分数：")
    try:
        score = int(score.strip())
        if not (0 <= score <= 100):
            raise ValueError('分数必须0-100之间')
        break
    except ValueError as e:
        print('输入有误,请重试')

if 80 <= score <= 100:
    print('优秀')
elif 70 <= score < 80:
    print('良好')
elif 60 <= score < 70:
    print('合格')
else:
    print('不合格')