import sys
input = sys.stdin.readline

def rec(S, v):
    if memo[S][v] != -1:
        return memo[S][v]
        
    if S == (1 << N) - 1:
        memo[S][v] = 0
        return 0
    
    res = -10 ** 18
    c = bin(S).count("1")
    
    for u in range(N):
        if not S >> u & 1:
            if c % 2 == 1:
                res = max(res, rec(S | 1 << u, u) + (A[v] ^ A[u]))
            else:
                res = max(res, rec(S | 1 << u, u))
    
    memo[S][v] = res
    
    return res

N = int(input())
A = list(map(int, input().split()))
memo = [[-1 for _ in range(N)] for _ in range(1 << N)]
ans = -10 ** 18

for i in range(N):
    ans = max(ans, rec(1 << i, i))

print(ans)