#include<iostream>
#include<iomanip>
using namespace std;
int main(){
	int n;
	cin>>n;
	if(n<10){
	cout<<"A"<<endl;
}else if(n>=10&&n<20){
	cout<<"B"<<endl;
}else if(n>=20&&n<40){
	cout<<"C"<<endl;
}else if(n>=40&&n<50){
	cout<<"D"<<endl;
}else if(n>=50&&n<80){
	cout<<"E"<<endl;
}


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