/*
    Author:zeke
    
    pass System Test!
    GET AC!!
*/
#include <iostream>
#include <queue>
#include <vector>
#include <iostream>
#include <vector>
#include <string>
#include <cassert>
#include <algorithm>
#include <functional>
#include <cmath>
#include <queue>
#include <set>
#include <stack>
#include <deque>
#include <map>
#include <iomanip>
#include <utility>
#include <stack>
using ll = long long;
using ld = long double;
using namespace std;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define all(x) (x).begin(), (x).end()
#define rep3(var, min, max) for (ll(var) = (min); (var) < (max); ++(var))
#define repi3(var, min, max) for (ll(var) = (max)-1; (var) + 1 > (min); --(var))
#define Mp(a, b) make_pair((a), (b))
#define F first
#define S second
#define Icin(s) \
    ll(s);      \
    cin >> (s);
#define Scin(s) \
    ll(s);      \
    cin >> (s);
template <class T>
bool chmax(T &a, const T &b)
{
    if (a < b)
    {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
bool chmin(T &a, const T &b)
{
    if (b < a)
    {
        a = b;
        return 1;
    }
    return 0;
}
typedef pair<ll, ll> P;
typedef vector<ll> V;
typedef vector<V> VV;
typedef vector<P> VP;
ll MOD = 1e9 + 7;
ll INF = 1e18;
vector<vector<int>> calcNext(const string &S)
{
    int n = (int)S.size();
    vector<vector<int>> res(n + 1, vector<int>(10, n));
    for (int i = n - 1; i >= 0; --i)
    {
        for (int j = 0; j < 10; ++j)
            res[i][j] = res[i + 1][j];
        res[i][S[i] - '0'] = i;
    }
    return res;
}
void add(long long &a, long long b)
{
    a += b;
    if (a >= MOD)
        a -= MOD;
}
ll n;
V vec;
ll RES = 0;
void cal(V vec2, V flag)
{
    if(vec2.size()==n){
        ll res = 0;
        for(int i=0;i<n;i+=2){
          //  cout<<vec[vec2[i]]<<" "<<vec[vec2[i+1]]<<" ";
            res ^= (vec[vec2[i]]+vec[vec2[i + 1]]);
        }
         chmax(RES, res);
    }else{
        ll f = -1;
        rep(i,n){
            if(!flag[i]){
                f = i;
                break;
            }
        }
        flag[f] = 1;
        vec2.push_back(f);
        rep(j,n){
            if(!flag[j]){
                vec2.push_back(j);
                flag[j] = 1;
                cal(vec2, flag);
                flag[j] = 0;
                vec2.pop_back();
            }
        }
        flag[f] = 0;
        vec2.pop_back();
    }
    return;
}
int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    cin >> n;
    vec.resize(n);
    rep(i, n) cin >> vec[i];
    V flag(n);
    V vec2;
    cal(vec2, flag);
    cout << RES << endl;
}