#include <bits/stdc++.h>
#define syosu(x) fixed<<setprecision(x)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> P;
typedef pair<double,double> pdd;
typedef pair<ll,ll> pll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<double> vd;
typedef vector<vd> vvd;
typedef vector<ll> vl;
typedef vector<vl> vvl;
typedef vector<string> vs;
typedef vector<P> vp;
typedef vector<vp> vvp;
typedef vector<pll> vpll;
typedef pair<int,P> pip;
typedef vector<pip> vip;
const int inf=1<<30;
const ll INF=1ll<<60;
const double pi=acos(-1);
const double eps=1e-8;
const ll mod=1e9+7;
const int dx[4]={-1,0,1,0},dy[4]={0,-1,0,1};

int n,res=0;
vi a,b;

void dfs(int I,int t){
	if(I==n+1){
		int tmp=0;
		vi c(n/2);
		for(int i=0;i<n;i++) c[b[i]]^=a[i];
		for(auto i:c) tmp+=i;
		res=max(res,tmp);
		return;
	}
	if(b[I]!=-1) dfs(I+1,t);
	else{
		b[I]=t;
		for(int i=I+1;i<n;i++) if(b[i]==-1){
			b[i]=t;
			dfs(I+1,t+1);
			b[i]=-1;
		}
		b[I]=-1;
	}
}

int main(){
	cin>>n;
	a=b=vi(n,-1);
	for(int i=0;i<n;i++) cin>>a[i];
	dfs(0,0);
	cout<<res<<endl;
}