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