import java.util.Scanner;

public class Main { public static void main(String[] args) { Scanner scanner = new Scanner(System.in); String grade =scanner.next();

    //write your code here......
      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");
                break;
        }

}

}