A14838. Quadratic Set

Let's call a set of positive integers $a_1, a_2, \dots, a_k$ quadratic if the product of the factorials of its elements is a square of an integer, i. e. $\prod\limits_{i=1}^{k} a_i! = m^2$ , for some integer $m$ .

You are given a positive integer $n$ .

Your task is to find a quadratic subset of a set $1, 2, \dots, n$ of maximum size. If there are multiple answers, print any of them.

A single line contains a single integer $n$ ( $1 \le n \le 10^6$ ).

In the first line, print a single integer — the size of the maximum subset. In the second line, print the subset itself in an arbitrary order.