#include <bits/stdc++.h>
using namespace std;
int main(){
    int a;
    cin>>a;
    if(a<10)
        cout<<"A";
    if(a>=10&&a<20)
        cout<<"B";
    if(a>=20&&a<40)
        cout<<"C";
    if(a>=40&&a<50) 
        cout<<"D";
    if(a>=50&&a<80)
        cout<<"E";
           
     
}
/**************************************************************
	Problem: 1044
	User: lijinkai
	Language: C++
	Result: Accepted
	Time:11 ms
	Memory:2072 kb
****************************************************************/