Limits: 833h20m0s, 512 MB

You will be given a tree of **N** nodes. Each node has a given value and the distance between adjacent nodes is **1** unit. Now you have to find how many pair of nodes exists whose sum will be **0** and the distance between them will be less than **L**.

This is a companion discussion topic for the original entry at https://toph.co/p/pairs-in-tree