#include<bits/stdc++.h>
using namespace std;

int main() {
	int n;
	cin>>n;
	if(n<10){
		cout<<"A";
	}else if(n>=10&&n<20){
		cout<<"B";
	}else if(n>=20&&n<40){
		cout<<"C"; 
	}else if(n>=40&&n<50){
		cout<<"D";
	}if(n>=50&&n<80){
		cout<<"E";
	} 
return 0;
}
/**************************************************************
	Problem: 1044
	User: linmiaoling
	Language: C++
	Result: Accepted
	Time:11 ms
	Memory:2072 kb
****************************************************************/