score = int ( input ( '请输入一个分数:' ) )
if 100 >= score >= 90:
print('A')
if 90 > score >= 80:
print('B')
if 80 > score >= 80:
print('C')
if 60 > score >= 0:
print('D')
if score < 0 or score > 100:
print('输入错误!')
score = int ( input ( '请输入一个分数:' ) )
if 100 >= score >= 90:
print('A')
if 90 > score >= 80:
print('B')
if 80 > score >= 80:
print('C')
if 60 > score >= 0:
print('D')
if score < 0 or score > 100:
print('输入错误!')