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




/**************************************************************
	Problem: 1044
	User: ct001
	Language: C++
	Result: Accepted
	Time:13 ms
	Memory:2072 kb
****************************************************************/