[n, n-1] [n-3, 3, n-1] [n-3, 2, 1, n-1] [n-3, 2, n] [n-1, n]
[n, n-1] [2, n-2, n-1] [2, n-3, 1, n-1] [2, n-3, n] [n-1, n]