Showing the process of merging edges when there is only one possible path. In (a), edge (1,3) could be followed by either (3,4) or (3,5) based on the reference markers. Edge (2,3) however can only be followed by (3,5). In (b), (2,3) and (3,5) are merged, which makes it possible to eliminate a marker from edge (1,3), and to merge it with (3,4). (c) shows the final state.