score = int(input('输入分数：'))
print("A" if score>89 else('B' if score>59 else 'C'))

while 1:
    score = int(input('输入分数：'))
    mark = [90,60,0]
    result=['A','B','C']
    for i in range(0,3):
        if score>=mark[i]:
            print('%d属于：%s'%(score,result[i]))
            break

def grade(score):
    if score >=90:
        print("A")
    elif score>=60:
        print("B")
    else:
        print("C")
while 1:
    score = int(input('输入分数：'))
    grade(score)