Does CEOI 2024 have an open competition? How can we register?

I just encountered a difficult problem with no solution. Can someone help me, thanks in advance.

Given a tree with N vertices. There are Q queries, the ith query is represented by K pairs (v, r), all vertices whose distance from v is not more than r will be marked. Ask how many vertices are marked per query. Limit N <= 5e4, Q <= 5e5 + N, the total K of all queries does not exceed 5e5 + N.