#yuki698

dp=[0]*(1<<14)
n=int(raw_input())
a=map(int,raw_input().split())
for i in xrange(1<<n):
 if bin(i).count("1")%2:
  continue
 for j in xrange(n):
  if i&(1<<j):
   continue
  for k in xrange(n):
   if i&(1<<k):
    continue
   dp[i|1<<j|1<<k]=max(dp[i|1<<j|1<<k],dp[i]+(a[j]^a[k]))
print dp[(1<<n)-1]