using System;

using System.Collections;

using System.Collections.Generic;

using System.Collections.Specialized;

class Person {

​

    public string FirstName { get; set; }

    public string LastName { get; set; }

    public DateTime DateOfBirth { get; set; }

    public Person () {

    }

​

    public Person(string f, string l) {

        FirstName = f;

        LastName = l;

    }

}

​

class Student : Person {

​

    public int StudentId { get; set; }

    public DateTime EnrollmentDate { get; set; }

    public DateTime? GraduationDate { get; set; }

​

    public Student (string firstname, string lastname) {

        FirstName = firstname;

        LastName = lastname;

    }

}

​

var Auri = new Student("Auri", "Rahimzadeh");

var Scott = new Student("Scott", "Jones");

var people = new List<Person>();

people.Add(Auri);

people.Add(Scott);

​

​