Problem - Company Queries II

Same company tree as before. Now, given two employees $a$ and $b$, find their lowest common boss (LCA). The LCA is the deepest node that is an ancestor of both $a$ and $b$. This is the first shared boss in their chains to the CEO.

You will use binary lifting to solve this in $O(\log n)$ per query. First equalize depths, then binary search upward for the divergence point. The $up$ table you already built for $k$-th ancestor works here too.