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

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