CF252A Little Xor

Little Petya likes arrays that consist of non-negative integers a lot. Recently his mom has presented him one such array consisting of $ n $ elements. Petya immediately decided to find there a segment of consecutive elements, such that the $ xor $ of all numbers from this segment was maximal possible. Help him with that. The $ xor $ operation is the bitwise exclusive "OR", that is denoted as "xor" in Pascal and "^" in C/C++/Java.

The first line contains integer $ n $ ( $ 1

Print a single integer — the required maximal $ xor $ of a segment of consecutive elements.

In the first sample one of the optimal segments is the segment that consists of the first and the second array elements, if we consider the array elements indexed starting from one. The second sample contains only one optimal segment, which contains exactly one array element (element with index three).