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

def p(sets, value):
    ans = []
    if not sets:
        return value
    m = min(sets)
    sets ^= {m}
    for nn in sets:
        ans.append(p(sets^{nn}, value+(A[m]^A[nn])))
    return max(ans)

sets = set(range(N))
print(p(sets, 0))