[[2, 5], [5, 6], [1, 4], [6, 8], [2, 6], [3, 6], [1, 10], [8, 9], [2, 3]]
[[1, 4, 10], [2, 5, 6, 3, 8, 9], [7]]
2
[[1, 2], [2, 7]]