Imagine a series of equally spaced holes running along a line infinitely in both directions. A groundhog is in one of the holes and every minute he jumps to a new hole that is some fixed interval of holes away from his current hole. You do not know where he starts, or the interval that he jumps, or the direction that he goes in, but after each of his moves you can shine a flashlight into one (and only one) hole. The problem is to find a method by which you can guarantee to eventually find the groundhog.