I'm searching the farest node for each node via one dfs and then try to answer the query using this information:

1) if(query_dist > distance_to_farest_node_from_query_vertex)
output 0
2) if query_vertex is ancestor of it's farest node then i return go_up_from(farest_node_from_query_vertex,
dist_to_far_node  -  query_dist)
3) if dist to lca(query_vertex,farest_node_from_query_vertex) enough (d(lca)>=query_dist) just go up from query_vertex in query_dist steps.
4) if(dist to lca is not enough) then go_up_from(
farest_node, farest_node_dist  -  query_dist)
my programm passes my tricky tests,sample test and test from thread. Pls, somebody, give me more tricky tests!

Edited by author 10.10.2010 22:43

ok, ac now  - i count LOG2N variable as floor(log2n) but i should set it ceil(log2n);

Thanks!
I was wondering why I got WA until I saw your reasons.
It gave me spirit,now I have got deeper realization of this problem.

Edited by author 01.12.2016 19:04