A = float(input(('Keep score :')))
B = float(input(('Midterm exam score:')))
C = float(input(('Final exam sscore')))
D = A+B+C
if (80<=D<=100):
    print('Grade A')
elif(75<=D,+79):
    print('Grade B+')
elif(70<=D<=74):
    print('Grade B')
elif(65<=D<=69):
    print('Grade C+')
elif(60<=D<=64):
    print('Grade C')
elif(55<=D<=59):
    print('Grade D+')
elif(50<=D<=54):
    print('Grade D')
elif(0<=D<=49):
    print('Grade F (fall)')