#include <bits/stdc++.h>
#define rep(i, a, n) for(int i = a; i < n; i++)
#define int long long
#define chmax(x, y) x = max(x, y)
using namespace std;
typedef pair<int, int> P;
const int INF = 1e15;
int dp[1LL << 14];

signed main(){
    int n;
    cin >> n;
    vector<int> a(n);
    rep(i, 0, n) cin >> a[i];
    for(int mask = 0; mask < (1LL << n); mask++){
        rep(i, 0, n){
            rep(j, i + 1, n){
                if(!(mask & (1LL << i)) && !(mask &(1LL << j))){
                    chmax(dp[mask + (1LL << i) + (1LL << j)], dp[mask] + (a[i]^a[j]));
                }
            }
        }
    }
    cout << dp[(1LL << n) - 1] << endl;
}