using System;

public class Nod

{

    public static void Main()

    {

        public int info;

        public Nod leg;

        public Nod(int val)

        {

            info = val;

            leg = null;

        }

    }

public class LSI

    {

        public Nod head;

        //constructor care initializeaza lista vida

        public LSI()

        {

            head = null;

        }

        //constructor care initializeaza lista cu un singur nod

        public LSI (int val)

        {

            head = new Nod(val);

        }

        // adauga un nod la inceputul listei

        public void AdInceput( int val)

        { 

            Nod p = new Nod ( val);

            p.leg = head;

            head = p;

        }

        public void AfisareLista()

        {

            for( Nod p = head; p != null; p=p.leg)

                Console.WriteLine(p.info + " ");

            Console.WriteLine();

        }

        // proprietate care determina nr de noduri

        public int Lungime

        {

            get

            {

                int cnt = 0;

                for ( Nod p = head; p != null; p=p.leg)

                    cnt++;

                return cnt;

            }

        }

        public override string ToString()

        {

            string S = " ";

            for ( Nod p = head; p != null; p=p.leg)

                S = S + p.info + " ";

            return S;

        }

        public void AdFinal ( int val)

        {

            Nod p, q;

            q = new Nod ( val );

                if(Lungime == 0)

                    head = q;

            // parcurg lista pana la ultimul nod

            // p va fi la ultimul nod din lista

            for (p = head; p.leg != null; p=p.leg)

                ;

            //leg p de nodul creat q

            p.leg = q;

        }

        //indexator

        public int this[int i]

        {

            get

            {

                if ( i < 0) return head.info;

                if (i >= Lungime ) i = Lungime - 1;

                // percurg lista sa ajunga pe nodul i;

                Nod p ;

                int k = 0;

                for( p = head; k < i; p = p.leg)

                    k++;

                return p.info;

            }

        }

        // functie membra (metoda)

        //insereaza dupa al k-lea nod un nou nod cu informatia val

        public void Insereaza ( int k , int val)

        { 

            Nod p,q;

            if ( k <= 0 ) // insereaza la inceput

            {

                AdInceput (val);

                return;

            }

            q=head;

            for ( p = head; p != null && k > 0; p=p.leg)

            {

                q=p;

                k--;

            }

            //inserez dupa nodul q

            p= new Nod (val);

            p.leg = q.leg;

            q.leg = p;

        }

        //elimina al k-lea nod daca k <= 0 sau k > nr de noduri atunci strgerea nu are loc

        public void Sterge ( int k)

        { 

            Nod p, q;

            if( k <= 0) return;

            if( k > Lungime ) return;

            if( k == 1) // sterg primul nod

            {

                p= head;

                head = head.leg; //head este al doilea

                p=null; // am sters primul nod

                return;

            }

            // cazul k > 1. Ma deplasez la al k=1 lea nod

            q= head;

            for ( p = head; k > 1; p=p.leg)

                k--;

            //Ma deplasez cu q la al k=1 lea nod

            // sterg nodul de dupa nodul q

            p= q.leg;

            q.leg = p.leg;

            p=null;

        }

}