using System;

public class Program

{

    public static void Main()

    {

       int grade;

        Console.WriteLine ("Enter the current grade number" );

        grade = Convert.ToInt32(Console.ReadLine());

        string  classification ;

        switch  (grade) 

        {

            case  1:

            case  2:    

            case  3:

            case  4:

            case  5:

                    classification = "grade-schooler" ;

                break;

            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 ) ;

        }

    }

}