#include <bits/stdc++.h>
using namespace std;
int main(){
int f;
cin>>f;
if (f<10){
	cout<<"A"<<endl; 
} else if(f>=10&&f<20){
	cout<<"B"<<endl;
}else if(f>=20&&f<40){
	cout<<"C"<<endl;
}else if(f>=40&&f<50){
	cout<<"D"<<endl;
}else if(f>=50&&f<80){
	cout<<"E"<<endl;
}
	return 0;
	}

/**************************************************************
	Problem: 1044
	User: mc002
	Language: C++
	Result: Accepted
	Time:10 ms
	Memory:2072 kb
****************************************************************/