### ggok's blog

By ggok, history, 3 years ago, ,

Hi, I recently came across this question and i have no idea how to approach it.

You are given a number N (3 ≤ N ≤ 100000) and you should create a permutation of the first N numbers.

The permutation should not have an arithmetic subsequence with three or more terms in it.

for example

5             4 2 3 1 5
3             3 1 2