#include <bits/stdc++.h>
#define rep(i,a,b) for(int i=a;i<b;i++)
#define rrep(i,a,b) for(int i=a;i>=b;i--)
#define fore(i,a) for(auto &i:a)
#define all(x) (x).begin(),(x).end()
using namespace std;
typedef long long ll;
typedef pair<int, int> P;
ll INF = 1e18;
ll MOD = 1e9 + 7;

int N, A[14], dp[1<<14];

int main() {
    cin >> N;
    rep(i, 0, N) cin >> A[i];

    rep(msk, 0, 1 << N) {
        rep(a, 0, N) rep(b, a+1, N) if(!(msk & (1<< a))) if(!(msk & (1 << b))) {
            dp[msk + (1 << a) + (1 << b)] = max(dp[msk + (1 << a) + (1 << b)], dp[msk] + (A[a] ^ A[b]));
        }
    }
    cout << dp[(1 << N) - 1] << endl;
}