[(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),(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)]
