n = input()
b = map(int,raw_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 i in xrange(n):
			ddd[dd[i]] ^= b[i]
		mx = max(mx,sum(ddd))
		return
	for i in xrange(n/2):
		if d[i] == 0:
			d[i] = 1
			dd[index]=i
			f(d,dd,index+1)
			d[i]=0
			break
	for i in xrange(n/2):
		if d[i] == 1:
			d[i] = 2
			dd[index]=i
			f(d,dd,index+1)
			d[i]=1

f(d,dd,0)
print mx