import java.util.Scanner;
public class Main{
    public static void main(String[]args){
        Scanner in = new Scanner(System.in);
        String grade = in.next();
        switch (grade)
        {
            case "A":
                System.out.println("优秀");
                break;
            case "B":
                System.out.println("良好");
                break;
            case "C":
                System.out.println("及格");
                break;
            case "D":
                System.out.println("不及格");
                break;
            default:
                System.out.println("未知等级");
        }
    }
}