The task is really not well written. It seems that it was written by a not very sane person. Because the example of 10 chairs and 10 patients was the most confusing. I realized that the essence lies in the difference of numbers. Well, like the first chair is occupied, then try to sit on another. I advise you to finalize the task, otherwise, the point is that they are trying not to explain the task to us, but to confuse it as much as possible, because if I would refer to their explanations, then, in general, my solution is completely wrong. By the way, I spent half a day because of three lines of code.