Can anyone expain to me why I am getting Memory Limit Exceeded in this problem:- https://codeforces.net/contest/29/problem/D. Here is the link to my submission:- https://codeforces.net/contest/29/submission/111265225.

I just computed the path between each pair of nodes (by inserting 1 at the front and 1 at the back of the leaf list) using lca technique. But getting MLE. Any help? Thanks for devoting your time in reading this.