static void Main(string[] args)
{
Department d1 = new Department("Computer Science", "CS");
Department d2 = new Department("Electrical Engg.", "EEE");
Student s1 = new Student("Rahim Kabir", "18-78969-2", 3.6f);
Student s2 = new Student("Abdul Haque", "18-78768-2", 3.2f);
Student s3 = new Student("Abul Kalam", "18-76754-2", 2.9f);
d1.AddStudent(s1, s2, s3);
s1.Department = d1;
s2.Department = d1;
s3.Department = d1;
s1.Department.ShowInfo();
d2.AddStudent(s3);
d1.AllStudents();
Console.WriteLine("***********************");
d2.AllStudents();
}