import operator
from functools import reduce
from itertools import compress
from sys import stdin

def pair(a):
    ret = []
    p = [0] * (len(a) // 2)
    def func(a, i):
        n = len(a)
        if n == 2:
            p[i] = a[0] + a[1]
            ret.append(reduce(operator.xor, p))
            return

        msk = [1] * n
        msk[0] = 0
        for j in range(1, n):
            msk[j] = 0
            x = list(compress(a, msk))
            p[i] = a[0] + a[j]
            func(x, i + 1)
            msk[j] = 1
    func(a, 0)
    return ret

def main():
    N = int(input())
    A = tuple(map(int, input().split()))

    ans = max(pair(A))
    print(ans)

input = lambda: stdin.readline()
main()