n=int(input())
a=list(map(int,input().split()))
ans=0
def f(now,a):
    global ans
    if len(a)==2:
        now+=a[0]^a[1]
        ans=max(ans,now)
        return
    for i in range(1,len(a)):
        f(now+a[0]^a[i],a[1:i]+a[i+1:])
f(0,a)
print(ans)