while True:
p = input("请输入一个五分制成绩(A、B、C、D、E): ")
if p.upper() == 'A':
print('90~100')
elif p.upper() == 'B':
print('80~89')
elif p.upper() == 'C':
print('70~79')
elif p.upper() == 'D':
print('60~69')
elif p.upper() =='E':
print('0~59')
else:
print('输入不正确,退出')
break