static void Main(string[] args)
{
var s = new Student("Alex");
s.SetKnowledge(new Knowledge(4));
University university = new University("CH.U.I.");
university.AddStudent(s);
university.AddStudent(new Student("Andrew Kostenko", new Knowledge(2)));
university.AddStudent(new Student("Julia Veselkina", new Knowledge(2)));
university.AddStudent(new Student("Maria Perechrest", new Knowledge(5)));
Internship internship = new Internship("Interlink");
internship.SelectStudentsFromUniversity(university);
Console.WriteLine("List of internship's students:");
Console.WriteLine(internship.GetStudents());
}