A8927. Maximum Xor Secondary

Bike loves looking for the second maximum element in the sequence. The second maximum element in the sequence of distinct numbers $x_{1},x_{2},...,x_{k}$ $(k>1)$ is such maximum element $x_{j}$ , that the following inequality holds: .

The lucky number of the sequence of distinct positive integers $x_{1},x_{2},...,x_{k}$ $(k>1)$ 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 $s_{1},s_{2},...,s_{n}$ $(n>1)$ . Let's denote sequence $s_{l},s_{l+1},...,s_{r}$ 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 $n$ $(1<n<=10^{5})$ . The second line contains $n$ distinct integers $s_{1},s_{2},...,s_{n}$ $(1<=s_{i}<=10^{9})$ .

Print a single integer — the maximum lucky number among all lucky numbers of sequences $s[l..r]$ .

For the first sample you can choose $s[4..5]={4,3}$ and its lucky number is $(4 xor 3)=7$ . You can also choose $s[1..2]$ .

For the second sample you must choose $s[2..5]={8,3,5,7}$ .