[(0,1),(1,2),(0,3),(1,3),(3,4),(4,5),(2,5),(4,6),(2,7),(6,8),(7,9),(8,9),(6,10),(10,11),(11,12),(10,12),(5,13),(8,13),(7,14),(12,15),(11,16),(13,17),(9,18)]
[(0,1),(0,2),(2,3),(1,3),(2,4),(1,4),(4,5),(3,5),(5,6),(6,7),(6,8),(7,9),(8,10),(7,10),(10,11),(8,12),(12,13),(11,13),(12,14),(9,15),(13,16),(11,17),(9,18)]
