Swapping

You are given a sequence $A_1, A_2, \ldots, A_N$. You may perform the following operation an arbitrary number of times (including zero): choose two adjacent elements of this sequence, i.e. $A_i$, $A_{i+1}$ for some valid $i$, and swap them. However, for each valid $i$, it is not allowed to choose $A_i$ (the element with the index $i$, regardless of its value at any point in time) more than once in