---

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

namespace Ticket_12
{
    class Program
    {
        internal class T
        {
            protected string Ts;

            public string ts
            {
                get
                {
                    return Ts;
                }
            }

            public T()
            {
                this.Ts = "T";    
            }

            public virtual void output()
            {
                Console.WriteLine("This is a {0} class", this.ts);
            }

            ~T(){}
        }

        internal class Y: T
        {
            public Y() : base()
            {
                this.Ts = "Y";    
            }

            public override void output()
            {
                Console.WriteLine("This is a {0} class", this.ts);
            }
        }

        internal class Client
        {
            private string s = "";

            public string S
            {
                get
                {
                    return s;
                }
            }

            public Client(string s)
            {
                this.s = "s";
            }

            public void showStr()
            {
                Console.WriteLine("Current value of g field of the Client: {0}", this.S);
            }
        }

        internal class Server
        {
            private static int n = 0;

            public int N
            {
                get
                {
                    return n;
                }
            }

            public Server(){}

            public void ShowState()
            {
                Console.WriteLine("Current number of clients connected to the Server: {0}", this.N);
            }

            public void AddClient(Client c)
            {
                n++;
                Console.WriteLine("The client {0} has added", c.S);
            }
        }

        static void Main(string[] args)
        {
            T t1 = new T();
            Y y = new Y();
            
            if (t1 is T) { t1.output();}
            t1 = new Y();
            if (t1 is Y) { t1.output(); }
            t1.GetType();
            
            t1 = new T();
            /*t1.output();
            y.output();

            ClassOutput(t1);
            ClassOutput(y);
            */
            Client c1 = new Client("Tom"), c2 = new Client("Jane"), c3 = new Client("Eugene");
            Server s = new Server();

            s.ShowState();
            s.AddClient(c1);
            s.AddClient(c2);
            s.AddClient(c3);
            s.ShowState();

            Console.ReadKey();
        }

        static public void ClassOutput(T t)
        {
            t.output();
        }
    }
}