using System;

public class task3

{

    public static void Main()

    {

        ListK<float> k = new ListK<float>();

        k.add(1);

        k.add(2);

        k.add(3);

        k.add(4);

        k.add(5);

        k.add(6);

        k.add(7);

        int l = k.length();

        for (int i = 0; i < l;i++) {

        Console.WriteLine(k[i]);

        }

        Console.WriteLine("\n");

        ListK<float> a = new ListK<float>();

        a.add(8);

        a.add(9);

        a.add(10);

         l = a.length();

        for (int i = 0; i < l;i++) {

        Console.WriteLine(a[i]);

        }

        Console.WriteLine("\n");

        a[1] = 9999;

        for (int i = 0; i < l;i++) {

        Console.WriteLine(a[i]);

        }

        Console.WriteLine("\n");

        a.union(k);

        l = a.length();

        for (int i = 0; i < l;i++) {

        Console.WriteLine(a[i]);

        }

    }

    class ListK<T>{

        private ListNode<T> head = null;

        class ListNode<T> {

            public readonly T Value;

            public readonly ListNode<T> Next;

            public ListNode(T val,ListNode<T> next){

                Value = val;

                Next = next;

            }

        }

        public void add(T obj) {

            if(head == null) {

                head = new ListNode<T>(obj,null);

            } else {

                head = new ListNode<T>(obj,head);

            }

        }

        public int length() {

            int i = 0;

            ListNode<T> h = head;

            while(h != null) {

                h = h.Next;

                i++;

            }

            return i;

        }

        public T this[int index]

        {

        get

        {

            int i = 0;

            ListNode<T> h = head;

            while(h != null) {

                if(i == index) {

                    return h.Value;

                }

                h = h.Next;

                i++;

            }

             throw new IndexOutOfRangeException();

        }

        set

        {

            if(index < 0 || index >= this.length())

            {

                throw new IndexOutOfRangeException();

            }

            int i = 0;

            ListNode<T> h = head;

            head = null;

            while(h!=null) {

                if(i == index){

                    this.add(value);

                } else {

                    this.add(h.Value);

                }

                h = h.Next;

                i++;

            }

            h = head;

            head = null;

            while(h != null){

                this.add(h.Value);

                h = h.Next;

            }

            return;

        }

    }

        public void union( ListK<T> list){

            ListNode<T> h = list.head;

            while (h != null){

                head = new ListNode<T>(h.Value,head);

                h = h.Next;

            }

            return;

        }

    }

}