package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func configure(scanner *bufio.Scanner) {
	scanner.Split(bufio.ScanWords)
	scanner.Buffer(make([]byte, 1000005), 1000005)
}
func getNextString(scanner *bufio.Scanner) string {
	scanned := scanner.Scan()
	if !scanned {
		panic("scan failed")
	}
	return scanner.Text()
}
func getNextInt(scanner *bufio.Scanner) int {
	i, _ := strconv.Atoi(getNextString(scanner))
	return i
}
func getNextInt64(scanner *bufio.Scanner) int64 {
	i, _ := strconv.ParseInt(getNextString(scanner), 10, 64)
	return i
}
func getNextFloat64(scanner *bufio.Scanner) float64 {
	i, _ := strconv.ParseFloat(getNextString(scanner), 64)
	return i
}
func main() {
	fp := os.Stdin
	wfp := os.Stdout
	extra := 0
	if os.Getenv("I") == "IronMan" {
		fp, _ = os.Open(os.Getenv("END_GAME"))
		extra = 100
	}
	scanner := bufio.NewScanner(fp)
	configure(scanner)
	writer := bufio.NewWriter(wfp)
	defer func() {
		r := recover()
		if r != nil {
			fmt.Fprintln(writer, r)
		}
		writer.Flush()
	}()
	solve(scanner, writer)
	for i := 0; i < extra; i++ {
		fmt.Fprintln(writer, "-----------------------------------")
		solve(scanner, writer)
	}
}
func solve(scanner *bufio.Scanner, writer *bufio.Writer) {
	n := getNextInt(scanner)
	m := mohu{}
	m.aa = make([]int, n)
	m.cc = make([]int, n/2)
	for i := 0; i < n; i++ {
		m.aa[i] = getNextInt(scanner)
	}
	ans = 0
	m.combination(0, 0, n, 0)
	fmt.Fprintln(writer, ans)
}

var ans int

type mohu struct {
	aa, cc []int
}

func (m *mohu) combination(c, l, n int, used uint32) {
	if c<<1 == n {
		m.permutation(0, n/2, 0, used)
		return
	}
	c++
	for i := l; i+(n/2-c) < n; i++ {
		m.combination(c, i+1, n, used|1<<uint(i))
	}
}

func (m *mohu) permutation(c, n int, used, pair uint32) {
	if c == n {
		j := 0
		k := 0
		x := 0
		cc := make([]int, n)
		dd := make([]int, n)
		for i := 0; i < n*2; i++ {
			if pair>>uint(i)&1 == 0 {
				cc[m.cc[j]] = m.aa[i]
				j++
				continue
			}
			dd[k] = m.aa[i]
			k++
		}
		for i := 0; i < n; i++ {
			x = x ^ (cc[i] + dd[i])
		}
		if ans < x {
			ans = x
		}
		return
	}
	for i := 0; i < n; i++ {
		if used>>uint(i)&1 == 1 {
			continue
		}
		m.cc[c] = i
		m.permutation(c+1, n, used|1<<uint(i), pair)
	}
}