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");
}
}
}