def set_pairings(n: int, yield_func):
    assert n > 0 and n % 2 == 0

    def rec(p, t, g):
        if p == n:
            pairs = []
            partners = [-1] * m
            for i in range(n):
                gid = g[i]
                if partners[gid] == -1:
                    partners[gid] = i
                else:
                    pairs.append((partners[gid], i))

            yield_func(pairs)
            return

        for i in range(m):
            x = t[i]
            if x == 2: continue
            t[i] += 1
            g[p] = i
            rec(p+1, t, g)
            t[i] -= 1
            if x == 0: break

    m = n // 2
    t = [0] * m  # 各グループの占領人数
    g = [0] * n  # t[i] : i 番目の人のグループ番号
    rec(0, t, g)


N = int(input())
A = list(map(int, input().split()))


def func(pairs):
    global ans
    res = 0
    for a, b in pairs:
        res ^= (A[a] + A[b])

    ans = max(ans, res)


ans = 0
set_pairings(N, func)
print(ans)