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