n = int(input())
lst = [int(a) for a in input().split()]

mx = 0
d = [0]*(n//2)
dd = [0]*n

def f(d,dd,index):
    global mx
    if index==n:
        ddd = [0]*(n//2)
        for a in range(n):
            ddd[dd[a]] ^= lst[a]
        mx = max(mx,sum(ddd))
        return
    
    for a in range(n//2):
        if d[a]==0:
            d[a]=1
            dd[index]=a
            f(d,dd,index+1)
            d[a]=0
            break
    
    for a in range(n//2):
        if d[a]==1:
            d[a]=2
            dd[index]=a
            f(d,dd,index+1)
            d[a]=1

f(d,dd,0)
print(mx)