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