using System;

public class Program

{

    public static void Main()

    {

        Person[] people = new Person[4] {

            new Student(), 

            new Student("Tej", 17, 111372), 

            new Teacher(), 

            new Teacher("Anna Sargsyan", 25, "Computer Science", 6)};

        foreach(Person person in people) {

            person.DisplayDetails();

        }

    }

}

​

public abstract class Person {

    public string Name = "Default";

    public int Age = 0;

    public abstract void DisplayDetails();

}

​

public class Student: Person {

    public int StudentId;

    public Student() {

        StudentId = 107156;

    }

    public Student(string name, int age, int id) {

        Name = name;

        Age = age;

        StudentId = id;

    }

    public override void DisplayDetails() {

        Console.WriteLine($"The student's name is {Name} and their age is {Age}; their id is {StudentId}");

    }

}

​

public class Teacher: Person {

    public string Subject;

    public int NumberPeriods;

    public Teacher() {

        Subject = "Default";

        NumberPeriods = 0;

    }

    public Teacher(string name, int age, string subject, int numberPeriods) {

        Name = name;

        Age = age;

        Subject = subject;

        NumberPeriods = numberPeriods;

    }

    public override void DisplayDetails() {

        Console.WriteLine($"The teacher's name is {Name} and their age is {Age}; they teach {Subject} for {NumberPeriods} periods.");

    }

}