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

namespace num
{
    class Node
    {
        public Node next;
        public int data;
        public int index;

        public Node() : this(null, 0, 0) { }

        public Node(int data, int index) : this(null, data, index) { }

        public Node(Node next, int data) : this(next, data, 0) { }

        public Node(Node next, int data, int index)
        {
            this.data = data;
            this.next = next;
            this.index = index;
        }
    }

    class OurList
    {
        private int size = 0;
        private Node root = null;
        private Node mirror(Node _temp)
        {
            Node temp = null;
            while (_temp != null)
            {
                temp = new Node(temp, _temp.data, _temp.index);
                _temp = _temp.next;
            }
            return temp;
        }

        public int Size
        {
            get => size;
            private set => size = value;
        }
        public void DeleteList()
        {
            root = null;
        }
        public void Add(int data, int index)
        {

            if (root == null)
            {
                ++size;
                root = new Node(data, index);

            }
            else if (index == Find(index).index)
            {
                Console.WriteLine("error index " + data + ":"+ index + " was already added" );
                return;
            }
            else
            {
                ++size;
                root = new Node(root, data, index);
            }

        }
        public void Add(int data)
        {
            if (root == null)
            {
                ++size;
                root = new Node(data, size);

            }
            else
            {
                ++size;
                root = new Node(root, data, size);

            }
        }
        public Node Find(int index)
        {
            Node save = new Node(-1, -1);
            Node temp = root;
            while (temp != null )
            {
                if (temp.index == index)
                    return temp;
                temp = temp.next;
            }
            return save;


        }
        public void Print()
        {
            Node temp = mirror(root);
            while (temp != null)
            {
                Console.WriteLine(" data:{0,5} index:{1,5}",temp.data,temp.index );
                temp = temp.next;
            }
            Console.WriteLine();
        }
        public void DeleteFirstElement()
        {
            root = First.next;
            root = First;
        }
        public Node First
        {
            get => mirror(root);
        }
        public override string ToString()
        {
            return base.ToString();
        }
    }

    class Program
    {
        static void Main(string[] args)
        {
            OurList a = new OurList();



            a.Add(15,4);
            a.Add(152);
            a.Add(123, 3);
            a.Add(1534, 25);
            a.Add(1534, 43);
            a.Add(1534, 20);
            a.Print();


        }
    }
}