import java.util.*;
public class Grade{
    public static void main(String[]args){
        Scanner in= new Scanner(System.in);
        System.out.println("Input score is: ");
        int ch=in.nextInt();
        char grade;
        ch=ch/10;
        switch(ch){
        case 9:{grade='A';break;}
        case 8:{grade='B';break;}
        case 7:{grade='C';break;}
        case 6:{grade='D';break;}
        default:grade='F';
        }
        System.out.println("Grade= "+grade);
    }

}