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

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