( Problem E ) Pikachu and Champions League

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Problem

Pikachu has already defeated so many legendary Pokemon, and is now organizing the Champions League where champions of all Conferences are going to battle for glory.

There are N Conferences around the world, connected by exactly N1 bidirectional roads. It is always possible to reach one Conference from another.

To choose the Champion of Champions, Pikachu chooses a set S of Conferences. Now, each Conference champion in S battles with every other Conference champion in S and for each battle, one of the champion has to travel. Pikachu wants to know the maximum distance any champion would travel to battle.

Pikachu has thought of Q such sets. He wants to know the maximum distance for each set so that he can choose the least tiresome set.

Constraints:

  • 2N500000
  • 1Q200000
  • It is always possible to reach one Conference from another
  • 2|S|500000
  • Sum of |S| over all Q sets is at most 500000
  • All elements in S are distinct

Input format:

  • First line contains two space separated integers N and Q
  • Next N1 lines contain two space separated integers, u and v (1u,vN), such that there is a path of length 1 between u and v
  • Next Q lines each starts with integer K, the number of elements in set followed by K distinct elements.

Output format:

  • Output Q lines, each of which contains maximum distance for the set of Conferences.
Time Limit: 4
Memory Limit: 512
Source Limit:
Explanation
  1. For the first query, the maximum distance is between pokemon 3 and 4.
  2. For the second query, the maximum distance is between pokemon 3 and 5.
  3. For the third query, the maximum distance is between pokemon 1 and 4.
  4. For the fourth query, the maximum distance is between pokemon 1 and 3.
  5. For the fifth query, the maximum distance is between pokemon 3 and 4.
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