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