using System;

public class Program

{

    public static void Main()

    {

        Console.WriteLine("PLease enter postcode");

        string postcode = Console.ReadLine();

        while (postcode.Length < 6 || postcode.Length > 8)

        {

            Console.WriteLine("INVALID POSTCODE - Please re-enter");

            postcode = Console.ReadLine();

        }

        Console.WriteLine("Valid Postcode");

    }

}