#include<bits/stdc++.h>
using namespace std;

int main(){
	int n;
	cin>>n;
	if(n>=90){
		cout<<"A"<<endl;
	}else if(n>=80){
		cout<<"B"<<endl;
	}else if(n>=70){
		cout<<"C"<<endl;
	}else if(n>=60){
		cout<<"D"<<endl;
	}else{
		cout<<"E"<<endl;
	}
	return 0;
}