#include<bits/stdc++.h>
using namespace std;
int main()
{
int r;
char s;
cin>>r;

if(r<10){
	s='A';
}else if(r<20){//100
	s='B';
}else if(r<40){
	s='C';
}else if(r<50){
	s='D';
}else if(r<80){
	s='E';
}

cout<<s<<endl;
return 0;
}

/**************************************************************
	Problem: 1044
	User: lbq001
	Language: C
	Result: Compile Error
****************************************************************/