Code compiles and runs fine in Workspace, but not in end of course C# Basics challenge. What's wrong?

using System;

namespace Treehouse.CodeChallenges
{
    class Program
    {
        static void Main()
        {
            int howMany = 0;
            while (true)
            {
              Console.Write("Enter the number of times to print \"Yay!\": ");
              try
              {
                howMany = Int32.Parse(Console.ReadLine());
                if (howMany < 0)
                {
                  Console.WriteLine("You must enter a positive number.");
                }
                else
                {
                  break;
                }
              }
              catch (FormatException)
              {
                Console.WriteLine("You must enter a whole number.");
              }
            }

            int i = 1;
            while (i <= howMany)
            {
              Console.WriteLine("Yay!");
              i += 1;
            }

        }
    }
}