Program.cs

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

namespace OOP3
{
    class Program
    {
        static void Main(string[] args)
        {
            Introducable human1 = new Human("Stoyan", 51);
           // Human ivan = new Human("Ivan", 16);
            Human.Nationality = "German";

            Introducable student1 = new Student("Ivan", 25, 12334);
            Introducable athlete1 = new Athlete("Petko", 25, "Futbol");

            human1.introduceYourSelf();
            student1.introduceYourSelf();
            athlete1.introduceYourSelf();

            Manager manager = new Manager(human1);
            manager.MakeHimIntroduceHimSelf();
            manager.Entity = student1;
            manager.MakeHimIntroduceHimSelf();
            manager.Entity = athlete1;
            manager.MakeHimIntroduceHimSelf();

            DoSomething();

            Console.WriteLine("The population of our virtual world is {0}", Human.Population);

            Console.Read();
        }

        static void DoSomething()
        {
            Human petko = new Human("Petko", 12);
            Human stoyan = new Human("Stoyan", 51);
        }
    }
}