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
    for a in combinations(A, N // 2):
        b = deque(set(A) - set(a))
        for _ in [0] * (N - 1):
            power = 0
            for x, y in zip(a, b):
                power += x ^ y
            ans = max(ans, power)
            b.rotate(1)
    print(ans)

main()