using System;

public class Program

{

    public static void Main()

    {

        int grade;

        string classification = "";

        string message = "The student is a ";

        Console.WriteLine("Enter the student's grade (6-12): ");

        grade = int.Parse(Console.ReadLine());

        switch(grade)

        {

            case 6:

            case 7:

            case 8:

                classification = "middle-schooler.";

                break;

            case 9:

                classification = "freshman.";

                break;

            case 10:

                classification = "sophomore.";

                break;

            case 11:

                classification = "junior.";

                break;

            case 12:

                classification = "senior.";

                break;

            default: 

                classification = "undefined";

                break;

​

        }

//      if(classification == "undefined")

//          Console.WriteLine("...invalid grade...");

//      else

//      {

//          Console.WriteLine("The student is a {0}", classification);

        message = message + classification;

//          Console.WriteLine(message);

//      }

        Console.WriteLine(classification == "undefined" ? "You entered an invalid grade." : message);

    }

}