from collections import deque
from itertools import combinations
from sys import stdin, stdout
input = lambda: stdin.readline().rstrip()
write = stdout.write

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

    ans = 0
    num = list(range(N))
    for n in combinations(num, N // 2):
        m = deque(set(num) - set(n))
        for _ in [0] * (N - 1):
            power = 0
            for i, j in zip(n, m):
                power += A[i] ^ A[j]
            ans = max(ans, power)
            m.rotate(1)
    print(ans)

main()