Sitting at a desk for twelve hours a day is not free. It costs you sleep quality, back health, attention span, and mood. The cheapest antidote is thirty minutes a day of moderate exercise.
Walking counts. A brisk walk after dinner, even in the last month before the exam, does more for your next study session than the extra thirty minutes at the desk would have.
Do not start a new sport in the last two months. This is not the time for a first attempt at basketball or a first long run. Injuries in June are the worst.
Team sports twice a week are useful for mood as much as for fitness — the social contact is a real part of the benefit.
In the last three days before the exam, keep moving gently but do not do anything that could injure you. A twisted ankle on June 6 is not a story you want.