import java.util.*;
public class main{
    public static void main(String[] args) {
        try{
            int a;
            Scanner in=new Scanner(System.in);
            a=in.nextInt();
            
            in.close();
            if(a>100)
            	System.out.print("");
            else if(a>=90)
            	System.out.print("A+");
            else if(a>=80)
            	System.out.print("A");
            else if(a>=70)
            	System.out.print("B"); 
            else if(a>=60)
            	System.out.print("C");
            else if(a>=0)
            	System.out.print("D");	
        }catch(Exception e){
            System.out.println("Input error!");
        }
    }
};