#include<bits/stdc++.h>
using namespace std;
int main() { 
  int n;
  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<50){
  	cout<<"D";
  	}else if(n>=50&&n<80){
  	cout<<"E";
    }return 0;
}
/**************************************************************
	Problem: 1044
	User: wangyousi
	Language: C++
	Result: Accepted
	Time:25 ms
	Memory:2072 kb
****************************************************************/