My Teacher gives me tricky riddles. Please help me (I will mark brainiest)

A guy came around the corner of a square lot and found a coin sitting on the ground, but did not pick it up. He kept walking and came across a penny, but did not pick it up, yet again. He kept walking and found yet again, a penny. He picked it up. He continued his walk a and discovered there were no more pennies, even when he went backwards, why?