public ClassRoom(Pupil pupil1, Pupil pupil2, Pupil pupil3)
     : this(pupil1, pupil2, pupil3, null)
 {
 }
 public ClassRoom(Pupil pupil1, Pupil pupil2, Pupil pupil3, Pupil pupil4)
 {
     pupils = new Pupil[] { pupil1, pupil2, pupil3, pupil4 };
 }
 public ClassRoom(Pupil pupil1, Pupil pupil2)
     : this(pupil1, pupil2, null, null)
 {
 }