import sys
input = sys.stdin.readline

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

for i in range(N):
    dp[(1<<N)-1][i] = 0

for S in range((1<<N)-2, -1, -1):
    for u in range(N):
        if not S >> u & 1:
            c = bin(S).count("1")
            for v in range(N):
                if c % 2 == 1:
                    dp[S][v] = max(dp[S][v], dp[S | 1 << u][u] + (A[v] ^ A[u]))
                else:
                    dp[S][v] = max(dp[S][v], dp[S | 1 << u][u])

ans = -10 ** 18

for i in range(N):
    ans = max(ans, dp[1 << i][i])

print(ans)