[BAEKJOON] 9498 : 시험 성적 - python3

A = int(input())
 
if (0 <= A <= 100):
    if A >= 90:
        print("A")
    elif A >= 80:
        print("B")
    elif A >= 70:
        print("C")
    elif A >= 60:
        print("D")
    else:
        print("F")