2. In the military drill formation performance, the students of a class happen to stand in a double-layer hollow square, with 9 students standing on each side of the outer layer. If the students of this class are to stand guard on a straight 250-meter long road, starting from one end and standing one person every 5 meters, then the number of students left after the road is fully occupied is $\qquad$ people.
answer: 5