# -*- coding: utf-8 -*-
"""
Created on Tue Aug 19 01:16:32 2025

@author: Maiku
"""

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

dp = [0 for _ in range(1<<N)]

for s in range(0, 1<<N, 2):
    for u in range(N):
        if (s >> u) & 1:
            continue
        for v in range(N):
            if (s >> v) & 1:
                continue
            #print(u, v)
            ns = s | (1<<u)
            ns = ns | (1<<v)
            dp[ns] = max(dp[ns], dp[s] + (A[u]^A[v]))

#print(dp)
print(dp[-1])