[(0,1),(0,2),(2,3),(2,4),(1,4),(3,5),(5,6),(1,7),(3,8),(6,9),(6,10),(10,11),(7,12),(4,13),(8,14),(8,15),(10,16),(9,17),(9,18),(5,19),(7,20)]
[(0,1),(0,2),(2,3),(3,4),(1,4),(3,5),(2,6),(4,7),(6,8),(7,9),(7,10),(10,11),(8,12),(8,13),(5,14),(9,15),(10,16),(5,17),(9,18),(1,19),(6,20)]
