#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>;

void solve() {
    int N;
    cin >> N;
    vi A(N);
    rep(i, N)cin >> A[i];

    vi dp(1 << N, INT_MIN / 3);
    dp[0] = 0;
    rep(S, 1 << N) {
        rep(i, N)if (!(S >> i & 1))rep(j, i)if (!(S >> j & 1)) {
            smax(dp[S | 1 << i | 1 << j], dp[S] + (A[i] ^ A[j]));
        }
    }
    cout << dp.back() << endl;
}

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