#include<bits/stdc++.h>
using namespace std;
int main(){ 
	int n;
	cin>>n;
	if(n>=90) cout<<"A"; 
	else if(n>=80) cout<<"B";  
	else if(n>=70) cout<<"C";  
	else if(n>=60) cout<<"D";  
	else  cout<<"E";   
	return 0;
}