#include<bits/stdc++.h>
using namespace std;
int main(){
	int a;
	cin>>a;
	if(a<10){
		cout<<"A";
	}else if(a>=10&&a<20){
		cout<<"B";
	}else if(a>=20&&a<40){
		cout<<"C";
	}else if(a>=40&&a<50){
		cout<<"D";
	}else if(a>=50&&a<80){
		cout<<"E";
	}
}
/**************************************************************
	Problem: 1044
	User: toughuatao1
	Language: C++
	Result: Accepted
	Time:12 ms
	Memory:2072 kb
****************************************************************/