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