#include<bits/stdc++.h>
using namespace std;
int main(){
	int i;
	cin>>i;
	if(i<10){
		cout<<"A";
	}
	if(i>10&&i<20){
		cout<<"B";
	}
	if(i>20&&i<40){
		cout<<"C";
	}
	if(i>40&&i<50){
		cout<<"D";
	}
	if(i>50&&i<80){
		cout<<"E";
	}
}
/**************************************************************
	Problem: 1044
	User: hongjiaming
	Language: C
	Result: Compile Error
****************************************************************/