#include<bits/stdc++.h>
using namespace std;
int main(){
	int N,A,B,C,D,E;
	cin>>N>>A>>B>C>>D>>E;
	if("N<10") cout<<"A";
	if("N>=10&&N<20") cout<<"B";
	if("N>=20&&N<40") cout<<"C";
	if("N>=40&&N<50") cout<<"D";
	if("N>=50&&N<80") cout<<"E";
	return 0;
}
/**************************************************************
	Problem: 1044
	User: lijinkai
	Language: C++
	Result: Compile Error
****************************************************************/