a=int(input("notunuzu giriniz:"))
if (a>=90):
    print("AA")
elif (a>=85):
    print("BA")
elif (a>=80):
    print("BB")
elif (a>=75):
    print("CB")
elif (a>=65):
    print("DC")
elif (a>=55):
    print("CC")
else: 
    print("FF kaldınız")