Build tree: 1-2, 1-3, 2-4, 2-5
// Initial: 5 separate nodes
link(2, 1) // 2's parent = 1
link(3, 1) // 3's parent = 1
link(4, 2) // 4's parent = 2
link(5, 2) // 5's parent = 2
Tree structure:
1
/ \
2 3
/ \
4 5
Now query path 4 to 3:
makeRoot(4) // 4 becomes root
access(3) // Path 4-2-1-3 in one aux tree
return aggregate of path
The path goes: 4 → 2 → 1 → 3 with length 4 (or sum of values).