using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ConsoleApp1
{
    class Integer
    {
        private Integer parent;

        public Integer()
        {
            parent = null;
        }

        public Integer (Integer incrementOperand)
        {
            parent = incrementOperand;
        }

        public bool IsZero => parent == null;

        public int ToInt()
        {
            if (IsZero) return 0;
            return 1 + parent.ToInt();
        }

        public static Integer FromInt(int x)
        {
            if (x < 0) throw new Exception("Eto neotritstelny tip!");
            if (x == 0) return new Integer(); //zero
            return new Integer(FromInt(x - 1));
        }

        public static Integer GetZero()
        {
            return new Integer();
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            Integer zero = Integer.GetZero();
            Integer one = new Integer(zero);

            Integer five = new Integer(new Integer(new Integer(new Integer(new Integer(Integer.GetZero())))));

            Console.WriteLine(zero.ToInt());
            Console.WriteLine(one.ToInt());
            Console.WriteLine(five.ToInt());
            Console.ReadKey();
        }
    }
}