using System;                   

public class Program

{

​

        public static void Main()

​

    {

Console.WriteLine("Please enter a positive integer.");

redo:

string input = Console.ReadLine();

ulong n;

if (ulong.TryParse(input, out n))

{

     if (n % 2 == 1)

        Console.WriteLine(n +  " is old ");

     else

        Console.WriteLine(n +  " is even " );

}

else 

   {Console.WriteLine("Please be sure to enter a positive integer.");

     goto redo;

   }

        }

}