They arrange your arrival one day before the selection process, and depart a day after you finish the medicals. Unless your destination has an evening flight, you can request to depart the same 4th day.
In the unlucky case of failing the first day, you have to arrange your departure on the second day, since the hotel will be covered only up to that night. (You can stay til the original departure date, but the hotel will be at your expense).
Cheers