scroce=int(input("輸入成績"))
if 90<= scroce <=100:
    grade="A"
elif 80 <= socroce <90:
    grade="B"
elif 70 <= socroce <80:
     grade="C"
elif 60<= socroce <70:
    grade="D"
else:
    grade="F"
print("成績是",grade)