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;
}
}
}

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