[BZOJ4543] [POI2014] Hotel enhanced version

## questions surface

https://darkbzoj.tk/problem/4543

Given an $ n $ points of the tree, looking for three points, so that they are equal in distance from the tree, find the number of programs.

$ N \ le $ 100000

## answer

IMHO, this question is really difficult.

First, the original title is $ n \ le 5000 $, and ye do anything,