Hi Liviu,
we must occupy the gym-room only 18 hours in the week, among the 35 hours of the week.
We don't have to fix the hours reserved: the important thing is that we can occupy the gym (in the morning) for only 18 hours, with our two teachers (one has 2+2+2+2+2+2+2+2+2 hours with his nine classes and the other has 2+2+2 hours with his three classes, so they must go togheter for 2+2+2 hours in the gym).
Thank you,
Guido.
you can add pseudo activities to occupy not allowed times.
Volker's idea sounds good, but maybe mine is faster and involves no headaches relating to dummy activities.
My ideas would go to use the versatile constraint activities occupy max time slots from selection. Add two rooms (because a room can hold a single activity at a single moment). Then, select all the 18+6 activities, selected slots = all time slots (or mornings, I am not sure), max occupied = 18.
Please let us know.