#include<bits/stdc++.h>
using namespace std;
int main(){
    int g;
    cin>>g;
    if(g<10){
    	cout<<"A";
    }else if(g>=10&&g<20){
    	cout<<"B";
    }else if(g>=20&&g<40){
    	cout<<"C";
    }else if(g>=40&&g<50){
    	cout<<"D";
    }else{
    	cout<<"E";
    } 
}
/**************************************************************
	Problem: 1044
	User: xuezihong1
	Language: C++
	Result: Accepted
	Time:12 ms
	Memory:2072 kb
****************************************************************/