///1.3.6.4

using System;

namespace homework
{
	class Program
	{
		public static void Main(string[] args)
		{
			tryParse();
			Console.ReadKey();
		}
		static int tryParse ()
		{
			Console.WriteLine(" please enter a number");
			begin:
			string value = Console.ReadLine();
			int number;
			bool result = Int32.TryParse(value, out number);

			while (!result)
			{
				Console.WriteLine("Error, enter a number");
				goto begin;
			}

			Console.WriteLine ("Ok, number is {0}", number);
			return number;
		}
	}
}