using System;

using System.Collections.Generic;

public interface ITeachable

$\{$

void Teach$()$;

$\}$

public interface IAdmin

$\{$

void Administrate$()$;

$\}$

public enum ResearchSpeciality

$\{$

AI$,$

QuantumComputing,

DataScience,

CyberSecurity

$\}$

public abstract class Staff

$\{$

public string Name $\{$ get; set; $\}$

public decimal Salary $\{$ get; set; $\}$

public Staff$($string name, decimal salary$)$

$\{$

Name $=$ name;

Salary $=$ salary;

$\}$

$\}$

public class Dean : Staff, ITeachable, IAdmin

$\{$

public Dean$($string name, decimal salary$)$ : base$($name$,$ salary$)\{\}$

public void Teach$()$

$\{$

Console.WriteLine$("$Dean is teaching."$)$;

$\}$

public void Administrate$()$

$\{$

Console.WriteLine$("$Dean is administrating."$)$;

$\}$

$\}$

public class Professor : Staff, ITeachable

$\{$

public string Class $\{$ get; set; $\}$

public Professor$($string name, decimal salary, string className$)$ : base$($name$,$ salary$)$

$\{$

Class $=$ className;

$\}$

public void Teach$()$

$\{$

Console.WriteLine$("$Professor is teaching."$)$;

$\}$

$\}$

public class Administrator : Staff, IAdmin

$\{$

public Administrator$($string name, decimal salary$)$ : base$($name$,$ salary$)\{\}$

public void Administrate$()$

$\{$

Console.WriteLine$("$Administrator is administrating."$)$;

$\}$

$\}$

public class Researcher : Staff, ITeachable

$\{$

public ResearchSpeciality Speciality $\{$ get; set; $\}$

public Researcher$($string name, decimal salary, ResearchSpeciality speciality$)$ : base$($name$,$ salary$)$

$\{$

Speciality $=$ speciality;

$\}$

public void Teach$()$

$\{$

Console.WriteLine$("$Researcher is teaching."$)$;

$\}$

$\}$

public class Department

$\{$

public string Name $\{$ get; set; $\}$

public List Staff $\{$ get; set; $\}$

public Department$($string name$)$

$\{$

Name $=$ name;

Staff $=$ new List$()$;

$\}$

$\}$

public class University

$\{$

public List Departments $\{$ get; set; $\}$

public University$()$

$\{$

Departments $=$ new List

$\{$

new Department$("$Math$"),$

new Department$("$English$"),$

new Department$("$Geography$"),$

new Department$("$Computer Science"$)$

$\}$;

$//$ Adding some default staff to each department

Departments$[0].$Staff.Add$($new Dean$("$Dr$.$ Smith", $120000))$;

Departments$[0].$Staff.Add$($new Professor$("$Prof$.$ Johnson", $90000,$ "Calculus"$))$;

Departments$[0].$Staff.Add$($new Administrator$("$Ms$.$ Brown", $60000))$;

Departments$[0].$Staff.Add$($new Researcher$("$Dr$.$ White", $80000,$ ResearchSpeciality.AI$))$;

$//$ Adding default staff to Geography department to avoid index out of range error

Departments$[2].$Staff.Add$($new Dean$("$Dr$.$ Green", $110000))$;

Departments$[2].$Staff.Add$($new Professor$("$Prof$.$ Blue", $85000,$ "Geography $101"))$;

Departments$[2].$Staff.Add$($new Administrator$("$Mr$.$ Yellow", $55000))$;

Departments$[2].$Staff.Add$($new Researcher$("$Dr$.$ Red", $75000,$ ResearchSpeciality.DataScience$))$;

$\}$

$\}$

public class Program

$\{$

public static void Main$()$

$\{$

var u $=$ new University$()$;

$//$ Accessing a valid index in Geography department

Console.WriteLine$($u$.$Departments$[2].$Staff$[3].$Name$)$;

$//$ Adding a new staff member to English department

u$.$Departments$[1].$Staff.Add$($new Researcher$("$Andy$",75000,$ ResearchSpeciality.DataScience$))$;

$//$ Additional test code

foreach $($var department in u$.$Departments$)$

$\{$

Console.WriteLine$($$"Department: $\{$department$.$Name$\}")$;

foreach $($var staff in department.Staff$)$

$\{$

Console.WriteLine$($$"Staff: $\{$staff$.$Name$\},$ Salary: $\{$staff$.$Salary$\}")$;

if $($staff is ITeachable teachable$)$

$\{$

teachable.Teach$()$;

$\}$

if $($staff is IAdmin admin$)$

$\{$

admin.Administrate$()$;

$\}$

$\}$

$\}$

$\}$

$\}$