import itertools
N = int(input())
A = list(map(int,input().split()))
C = list(itertools.combinations(range(N), N//2))
ans = 0
for c in C:
    r = list(range(N))
    for i in c:
        r.remove(i)
    P = list(itertools.permutations(r))
    for p in P:
        power=0
        for i in range(N//2):
            power+=A[c[i]]^A[p[i]]
        ans = max(power,ans)
print(ans)