private static List<Student> _students = new List<Student>();
        static public void AddStudent()
        {
            bool again = true;
            try
            {
                Console.Clear();
                Console.WriteLine("UIS - ADDING A NEW STUDENT");
                Console.WriteLine("---------------------------");

                Console.Write("Enter student name: ");
                string name = Console.ReadLine();
                Console.Write("Enter student's last name: ");
                string surname = Console.ReadLine();
                Console.Write("Enter the specialty of the student: ");
                string specialty = Console.ReadLine();
                Console.Write("Enter the year of birth of the student: ");

                while (again)
                {
                    string input = Console.ReadLine();
                    if (Int32.TryParse(input, out int year))
                    {
                        Student newStundent = new Student(name, surname, specialty, year);
                        _students.Add(newStundent);
                        Console.WriteLine("\nCreated " + newStundent);
                        again = false;
                    }
                    else
                    {
                        Console.WriteLine("Please enter the number!");
                        Console.ReadKey();

                        Console.Clear();
                        Console.WriteLine("UIS - ADDING A NEW STUDENT");
                        Console.WriteLine("---------------------------");
                        Console.WriteLine("Enter student name: " + name);
                        Console.WriteLine("Enter student's last name: " + surname);
                        Console.WriteLine("Enter the specialty of the student: " + specialty);
                        Console.Write("Enter the year of birth of the student: ");
                    }
                }
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
                Console.ReadKey();
            }
        }