According to my experience, the canteen is the most chaotic of the three scenes, so we must be very careful. If you take a seat in the canteen, you can take out the books in your bag and take a seat. Don't put the bag (it's dangerous, even if there are no valuables). It is best to carry it with you; In classrooms and libraries, it is relatively safe. As long as you carry valuables such as money and mobile phone with you, the bag can be placed on the table or where the camera can see it. Don't be too close to the door. It should be no problem.