A dog can run only halfway into the woods. After the halfway mark, if the dog continues to run it will be running out of the woods.
This is a trick question and has nothing to do with the running ability of a dog. If the woods are deep enough and the dog has enough stamina, it will continue to run even beyond the halfway point. A well trained dog is guided by its training and instinct. It will not stop until ordered to do so by its master. All the dog needs is a little rest, some food and water.