#include<bits/stdc++.h>
using namespace std;
int main(){
	int x;
	cin>>x;
	if(x<10)
		cout<<"A";
	if(x>=10 && x<20)
		cout<<"B";
	if(x>=20 && x<40)
		cout<<"C";		 
	if(x>=40 && x<50)
		cout<<"D";	
	if(x>=50 && x<80)
		cout<<"E";		
		
	return 0;
}
/**************************************************************
	Problem: 1044
	User: cyp
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/