#include<bits/stdc++.h>
using namespace std;
int main(){
	int x;
	cin>>x;
	if(x<60){
		cout<<"D";
	}else if(x>=60&&x<75){
		cout<<"C";
	}else if(x>=75&&x<=85){
		cout<<"B";
	}else if(x>=85&&x<95){
		cout<<"A";
	}else if(x>=95&&x<=100){
		cout<<"A+";
	}
	return 0;
}