#define _USE_MATH_DEFINES
#pragma region include
#include <iostream>
#include <iomanip>
#include <stdio.h>

#include <sstream>
#include <algorithm>
#include <iterator>
#include <cmath>
#include <complex>

#include <string>
#include <cstring>
#include <vector>
#include <bitset>

#include <queue>
#include <set>
#include <map>
#include <stack>
#include <list>

#include <ctime>
////
//#include <random>//
#pragma endregion //#include
/////////

#pragma region typedef
typedef long long LL;
typedef long double LD;
typedef unsigned long long ULL;
#pragma endregion //typedef
////定数
const int INF = (int)1e9;
const LL MOD = (LL)1e9+7;
const LL LINF = (LL)4e18+20;
const LD PI = acos(-1.0);
const double EPS = 1e-9;
/////////
using namespace::std;

int N;
vector<int> A;
LL ans;
void dfs(int s,LL val){
	int a=-1;
	int b=-1;
	for(int i=0;i<N;++i){
		if( (s&(1<<i)) == 0 ){
			a = i;
			s ^= (1<<a);
			break;
		}
	}
	if(a==-1){
		ans = max(ans,val);
		return;
	}
	for(int i=0;i<N;++i){
		if( (s&(1<<i)) == 0 ){
			b = i;
			dfs( s^(1<<b), val^(A[a]+A[b]) );
		}
	}
}
void solve(){
	ans = 0;
	cin>>N;
	A = vector<int>(N);
	for(int i=0;i<N;++i){
		cin>>A[i];
	}
	dfs(0,0);

	cout << ans << endl;
}

#pragma region main
signed main(void){
	std::cin.tie(0);
	std::ios::sync_with_stdio(false);
	std::cout << std::fixed;//小数を10進数表示
	cout << setprecision(16);//小数点以下の桁数を指定//coutとcerrで別	

	solve();
}
#pragma endregion //main()