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