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


def dfs(tot, used):
    if used == (1 << N) - 1:
        return tot

    res = 0
    for i in range(N):
        if used >> i & 1:
            continue
        for j in range(i + 1, N):
            if used >> j & 1:
                continue
            tmp = dfs(tot + (A[i] ^ A[j]), used | 1 << i | 1 << j)
            res = max(res, tmp)
        break
    return res


print(dfs(0, 0))