The interactor of problem 1815B can be made TLE.

Select a case that n>800,add O(n) random x between n/2 and 3n/2, and query n random pairs of nodes.As there are O(n^2) edges in the graph, it takes O(n^2) time to bfs and O(n^3) time for the interactor to answer all queries.

Submission:https://mirror.codeforces.com/contest/1815/submission/201700734