#include <bits/stdc++.h>

#define REP(i, n) for (int i = 0; i < n; i++)
#define llINF ((long long)1e18)
#define iINF ((int)1e9)
#define ALL(obj) obj.begin(), obj.end()

using namespace std;

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

int rec(int S) {
    if (dp[S] != -1) {
        return dp[S];
    }

    if (S == (1 << N) - 1) {
        return 0;
    }

    int res = 0;

    REP(i, N) {
        if ((S >> i) & 1) continue;
        REP(j, N) {
            if ((S >> j) & 1) continue;
            res = max(res, rec(S | (1 << i) | (1 << j)) + (A[i] ^ A[j]));
        }
    }
    return dp[S] = res;
}

int main() {
    cin >> N;
    REP(i, N) { cin >> A[i]; }
    memset(dp, -1, sizeof(dp));
    cout << rec(0) << endl;
}