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

int main(){
	int n;
	cin>>n;
	if(n<10){
		cout<<"A";
	}
	if(n>=10&&n<20){
		cout<<"B";
	}
	if(n>=20&&n<40){
		cout<<"C";
	}
	if(n>=40&&n<50){
		cout<<"D";
	}
	if(n>=50&&n<80){
		cout<<"E";
	}
}

/**************************************************************
	Problem: 1044
	User: linzihang
	Language: C++
	Result: Accepted
	Time:12 ms
	Memory:2072 kb
****************************************************************/