import sys
readline = sys.stdin.readline

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

dp = [0] * (1 << N)
# dp[S] = 集合Sを使用済みのときの最大戦闘力

for status in range(1 << N):
  for i in range(N): # 一人目の選択
    if (status >> i) & 1:
      continue
    for j in range(N):
      if (status >> j) & 1:
        continue
      xor = A[i] ^ A[j]
      next_status = status | (1 << i) | (1 << j)
      if dp[next_status] < dp[status] + xor:
        dp[next_status] = dp[status] + xor

print(dp[-1])