from itertools import combinations, permutations
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 n1 in combinations(num, N // 2):
        m = set(num) - set(n1)
        for n2 in permutations(m, N // 2):
            power = 0
            for i, j in zip(n1, n2):
                power += A[i] ^ A[j]
            ans = max(ans, power)
    print(ans)

main()