You have a bag which contains n cards. There is a number written on each card; the number on i-th card is ai.

You are given a tree

把先前信息低的两篇blog给拆了,这样好点.

Today, as a friendship gift, Bakry gave Badawy n integers a1,a2,…,an and challenged him to choose an integer X such that the value max1≤i≤n(ai⊕X) is minimum possible, where ⊕ denotes the bitwise XOR operation.

As always, Badawy is too lazy, so you decided to help him and find the minimum possible value of max1≤i≤n(ai⊕X).