# -*- coding: utf-8 -*-
"""
Created on Mon Aug  3 14:28:48 2020

@author: AE401
"""

score=input("please enter your score:")
score=int(score)
if score>=0 and score<=100:
    if score>=90:
        print('A')
    elif score>=80:
        print('B')
    elif score>=70:
        print('C')
    elif score>=60:
        print('D')
    else:
        print('E')
else:
    print("please enter the correct score.")