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