score = int (input("score："))
if score > 90:
  print("A")
elif score > 80:
  print("B")
elif score > 70:
  print("C")
elif score > 60:
  print("D")
else score < 60:
  print("加油吧孩纸")

'''
条件测试
'''
#单个条件测试
age0 = 22
print(age0>=22) # True

#多个条件测试 and
age0 = 22
age1 = 18
print(age0>=21 and age1>=21) #False

#多个条件测试 or
print(age0>=21 or arg0>=21) #True
 
#in和not in（检查特定值是否在列表中）
fruits = ['apple','banana','orange']
print('apple' in fruits) #True
print('apple' not in fruits) #False

'''
简单的if语句（仅包含一个测试和一个操作）
'''
height = 1.7
if height>=1.3:
  print('高')

'''
if-else
'''
height = 1.8
if height<=1.4:
  print('免票')
else:
  print('全票')
#最后输出全票

'''
if-elif
'''
height = 1.5
if height>=1.4:
  print('嘿嘿')
elif height>=1.3:
  print('呵呵')
#最后输出嘿嘿

'''
if-elif-else
'''
height = 1.8
if height<=1.4:
  print('免票')
elif height>1.4 and height<=1.7:
  print('半票')
else:
  print('全票')
#最后输出全票