a = int(input()) 
if a<10:
    print('A')
elif a<20:
    print('B')
elif a<40:
    print('C')
elif a<50:
    print('D')
elif a<80:
    print('E')

/**************************************************************
	Problem: 1044
	User: admin
	Language: Python
	Result: Accepted
	Time:139 ms
	Memory:34244 kb
****************************************************************/