AP On Trees

You are given a [tree](https://en.wikipedia.org/wiki/Tree_(data_structure)) with $N$ nodes, where the $i^{th}$ node has a value $A_i$ associated to it. You need to answer $Q$ queries. Each query is of the form: - $X$ $Y$ : Given two nodes $X$ and $Y$ $(1\le X,Y\le N)$, find the length of the **longest** [arithmetic progression](https://en.wikipedia.org/wiki/Arithmetic_progression) formed using th