#define _USE_MATH_DEFINES
#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define MT make_tuple
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
#define RT return
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
using vll = vector<ll>;

const int MAX_N = 14;
int N, A[MAX_N];
int ans;

void f(int S, int sm) {
    if (S == ((1<<N) - 1)) {
        smax(ans, sm);
        return;
    }

    int p = -1;
    rep(i, N)if (!(S >> i & 1)) {
        p = i;
        break;
    }
    FOR(i, p + 1, N)if (!(S >> i & 1)) {
        f(S | 1 << p | 1 << i, sm ^ (A[i] + A[p]));
    }
}

void solve() {
    cin >> N;
    rep(i, N)cin >> A[i];
    f(0, 0);
    cout << ans << endl;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(15);
    solve();
    return 0;
}