Maximum Xor Secondary
题目描述
Bike loves looking for the second maximum element in the sequence. The second maximum element in the sequence of distinct numbers x1,x2,...,xk (k>1) is such maximum element xj, that the following inequality holds: 
.
The lucky number of the sequence of distinct positive integers x1,x2,...,xk (k>1) is the number that is equal to the bitwise excluding OR of the maximum element of the sequence and the second maximum element of the sequence.
You've got a sequence of distinct positive integers s1,s2,...,sn (n>1). Let's denote sequence sl,sl+1,...,sr as s[l..r] (1≤l<r≤n). Your task is to find the maximum number among all lucky numbers of sequences s[l..r].
Note that as all numbers in sequence s are distinct, all the given definitions make sence.
The first line contains integer n (1<n≤105). The second line contains n distinct integers s1,s2,...,sn (1≤si≤109).
Print a single integer − the maximum lucky number among all lucky numbers of sequences s[l..r].
5
5 2 1 4 3
7
5
9 8 3 5 7
15
For the first sample you can choose s[4..5]={4,3} and its lucky number is (4xor3)=7. You can also choose s[1..2].
For the second sample you must choose s[2..5]={8,3,5,7}.
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