using System;

public class Program

{

    public static void Main()

    {

         Console.WriteLine ("Input a number: ");

         string number = Console.ReadLine();

        switch (number)

        {

         case "ones":

            Console.WriteLine("Single-digit numbers only");

            break;

         case "tens":

            Console.WriteLine("Two-digit numbers only");

            break;

         case"hundreds":

            Console.WriteLine("Three-digit numbers only");

            break;

        default:

            Console.WriteLine("invalid");

            break;

    }

            Console.ReadLine();

    }

}