B'This is an interactive problem. You 're given a tree consisting of n nodes, rooted at node 1 . A tree is a connected graph with no cycles. We chose a hidden node x . In order to find this node, you can ask queries of two types: Node a is called an ancestor of node b if a ne b and the shortest path from node 1 to node b passes through node a . Note that in this problem a node is not an ancestor of itself. Can you find x in no more than 36 queries? The hidden node is fixed in each test beforehand and does not depend on your queries. The first line contains the integer n ( 2 <= n <= 2 cdot 10^5 ) -- the number of nodes in the tree. Each of the next n-1 lines contains two space-separated integers u and v ( 1 <= u,v <= n ) that mean there 's an edge between nodes u and v . It 's guaranteed that the given graph is a tree. To print the answer, print "! x" (without quotes). To ask a question, print it in one of the formats above: After each question, you should read the answer: either the distance or the second vertex on the path, as mentioned in the legend. If we answer with -1 instead of a valid answer, that means you exceeded the number of queries, made an invalid query, or violated the condition in the second type of queries. Exit immediately after receiving -1 and you will see Wrong answer verdict. Otherwise, you can get an arbitrary verdict because your solution will continue to read from a closed stream. After printing a query, do not forget to output end of line and flush the output. Otherwise, you will get Idleness limit exceeded. To do this, use: Hacks: The first line should contain two integers n and x ( 2 <= n <= 2 cdot 10^5 , 1 <= x <= n ). Each of the next n-1 lines should contain two integers u and v ( 1 <= u,v <= n ) that mean there is an edge between nodes u and v$$'...