5.1.2 After some time spent in a bar, Peter starts to walk home. Suppose that the streets form a rectangular grid. Peter always walks to the nearest comer and then decides on the direction of the next segment of his walk (so that he never changes direction in the middle of the block). Define the “state of the system” in such a way as to accommodate conveniently the assumption that Peter never goes directly back to the comer he just left.