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

/**************************************************************
	Problem: 1044
	User: ljl2
	Language: C++
	Result: Accepted
	Time:11 ms
	Memory:2072 kb
****************************************************************/