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