from operator import xor
from collections import deque
from functools import reduce
from sys import stdin

def pair(lst):
    def func(a, b):
        n = len(a)
        if n == 2:
            ret.append(reduce(xor, b + [a[0] + a[1]]))
            return
        a0 = a.popleft()
        for _ in [0] * (n - 1):
            ai = a.popleft()
            arg2 = b + [a0 + ai]
            func(a.copy(), arg2)
            a.append(ai)
    lst = deque(lst)
    ret = []
    func(lst, [])
    return ret

def main():
    input = lambda: stdin.readline()
    N = int(input())
    A = list(map(int, input().split()))

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

main()