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.

小Petya非常喜欢由非负整数组成的数组。最近，他的妈妈送给他一个包含 $n$ 个元素的此类数组。Petya立刻决定在其中找出一个连续子段，使得该子段中所有数的异或（xor）值尽可能大。请帮他解决这个问题。

异或（xor） 运算即按位异或（exclusive OR），在 Pascal 中记作 xor，在 C/C++/Java 中记作 ^。

The first line contains integer n (1 ≤ n ≤ 100) — the number of elements in the array. The second line contains the space-separated integers from the array. All numbers are non-negative integers strictly less than 230.

第一行包含一个整数 $n$（$1 \leq n \leq 100$）—— 表示数组中元素的个数。
第二行包含用空格分隔的数组中的整数。所有数字均为非负整数，且严格小于 $2^{30}$。

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

输出一个整数——该连续子段元素所能达到的最大 xor 值。

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).

在第一个样例中，一个最优区间是由数组的第1个和第2个元素组成的区间（假设数组下标从1开始）。

第二个样例中仅存在一个最优区间，该区间恰好包含一个数组元素（即下标为3的元素）。