أنشطة تبدأ يوم الطلاب أو تنهيه

[Liviu Lalescu]

You need to divide the students according to categories, students who have B and students who don't have B. Then adding max 0 gaps for both of these students will ensure that both of them will not have gaps. So activities for students who don't have B will not bring gaps, so B will either be in the beginning, in the end, or on a separate day.

[ghani1990]

Oh, I understand now.
It's an innovative idea.
thank you very much

[Liviu Lalescu]

You are welcome!