Given a **rooted** tree with **N** nodes where each node has a value, find a pair of nodes **(u, v)** so that **u** is an **ancestor** of **v** and the bit-wise **XOR** of the values of **u** and **v** is the maximum among all such pairs. The tree is always rooted at node **1**.

This is a companion discussion topic for the original entry at https://toph.co/p/yet-another-xor-problem