from itertools import combinations


def solve(N, A):
    dp = [-float("inf")] * (1 << N)
    dp[0] = 0
    for V in range(1 << N):
        for i, j in combinations(range(N), 2):
            ai = A[i]
            aj = A[j]
            if not ((V >> i) & 1) and not ((V >> j) & 1):
                VV = V | (1 << i) | (1 << j)
                dp[VV] = max(dp[VV], dp[V] + (ai ^ aj))

    return dp[-1]


def main():
    N = int(input())
    A = list(map(int, input().split()))
    ans = solve(N, A)
    print(ans)


if __name__ == "__main__":
    main()