#include<bits/stdc++.h>
using namespace std;
int n;
int main(){
	cin>>n;
	if(n<10){
		cout<<"A";
	}
	else if(n>=10&&n<20){
		cout<<"B";
	}
	else if(n>=20&&n<40){
		cout<<"C";
	}
	else if(n>=40&&n<60){
		cout<<"D";
	}
	else{
		cout<<"E";
	}
	return 0;
}

/**************************************************************
	Problem: 1044
	User: chenzelin
	Language: C++
	Result: Accepted
	Time:16 ms
	Memory:2072 kb
****************************************************************/