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| # | Title | Points | Solved | Admin | |
|---|---|---|---|---|---|
This is an interactive problem.
There is a hidden simple undirected graph with vertices .
The graph is connected. Also, among every distinct vertices, there is at least one pair of adjacent vertices.
Your goal is to find a simple path containing at least vertices.
You may ask at most queries.
In one query, you choose a vertex and a non-empty set of vertices. The interactor returns one vertex from that is adjacent to in the hidden graph. If there is no such vertex, the interactor returns .
If there are several valid vertices that can be returned, the interactor may return any of them.
The hidden graph is fixed before the interaction starts.
The interaction starts with the interactor printing one integer .
You may ask at most queries.
To ask a query, print a line in the following format:
Here , , and must be distinct vertices different from .
After this, the interactor prints one integer .
If there is at least one vertex in adjacent to , then is one such vertex. If there are several possible choices, the interactor may return any of them.
If no vertex in is adjacent to , then .
To give the final answer, print a line in the following format:
The vertices must be distinct, every two consecutive vertices must be adjacent in the hidden graph, and must be at least .
After printing each query or the final answer, flush the output.
In this sample, the hidden graph has edges and .
The first line of the input gives . After the query , the interactor returns . After the query , the interactor returns .
The user asks queries.
The final answer gives the path . This path has vertices, while the required length is at least .
In this sample, the hidden graph has edges , , , , , , , and .
The first line of the input gives . The next lines are the interactor responses to the user's queries, in order: , , , , , and .
The user asks queries.
The final answer gives the path . This path has vertices, while the required length is at least .