You are given a permutation $$$p$$$ of $$$[1, 2, \ldots, n]$$$. It is guaranteed that $$$n$$$ is even.

You can perform the following operation on it:

• Select a subsequence (say $$$t$$$) of length $$$2k$$$ (where $$$k$$$ does not need to be the same across operations) such that either

• Then, remove every element of $$$t$$$ from $$$p$$$. You want to make $$$p$$$ empty using the minimum number of operations.

Is this problem new, if not could you kindly share the link?