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

	int n;
	cin>>n;
	
	if(n<10){
		cout<<"A"<<endl;
	}else if(n<20){
		cout<<"B"<<endl;
	}else if(n<40){
		cout<<"C"<<endl;
	}else if(n<50){
		cout<<"D"<<endl;
	}else if(n<80){
		cout<<"E"<<endl;
	}


	return 0;
}

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