from itertools import *

def popcount(n):
    cnt = 0
    while n:
        cnt += n & 1
        n //= 2
    return cnt

N = int(input())
A = list(map(int, input().split()))
ans = 0
N2 = 1 << N
for s in range(N2):
    if popcount(s) != N//2:
        continue
    one = []
    zero = []
    for i in range(N):
        if (s >> i) & 1:
            one.append(i)
        else:
            zero.append(i)
    
    for tup in permutations(one):
        val = 0
        for i in range(N//2):
            val ^= A[tup[i]] + A[zero[i]]
        ans = max(ans, val)
print(ans)