A classical mechanics problem by A Former Brilliant Member

A car is moving at a constant speed of $40 \text{ km/hr}$ along a straight road which heads towards a large vertical wall and makes a sharp $90^\circ$ turn by the side of the wall. A fly on the wall starts flying at a constant speed of $100 \text{ km/hr}$ when the car is $20\text{ km}$ away, flies until it reaches the glass pane of the car and returns to the wall at the same speed. It continues to fly between the car and the wall till the car makes the $90^\circ$ turn.

Find the number of trips it has made between the car and the wall. If you think the answer is infinite enter 12345 as answer.