Hi,
Consider a rooted tree
size(v) = number of vertices in subtree of v
Any good limit on $$$\sum_{i=1}^{n} $$$$$$\sqrt{size(i)}$$$ ?
like
$$$O(N*LOG)$$$
$$$O(N*LOG(LOG))$$$
$$$O(N)$$$
...
UPD :
b(v) is a son of v with the largest subtree size.
limit on $$$\sum_{i=1}^{n} $$$$$$\sqrt{size(i) - size(b(i))}$$$