#include <iostream>
#include <stdio.h>
#include <string.h>
#include <vector>
#include <string>
#include <set>
#include <map>
#include <algorithm>
#include <numeric>
#include <queue>
#include <cassert>
#include <cmath>
#include <bitset>
#include <cctype>
using namespace std;

void chmax(long long& a, long long b) {
    a = max(a, b);
}
int n;
int a[16];
int ans = 0;

void dfs(vector<int> v, vector<bool> used) {
    if (v.size() == n) {
        int res = 0;
        for (int i = 0; i < n; i += 2) res += a[v[i]] ^ a[v[i+1]];
        //printf("v : "); for (int i = 0; i < n; i++) printf("%d ", v[i]); printf("\n");
        //printf("res = %d\n", res);
        ans = max(ans, res);
        return;
    }

    if (v.size() % 2 == 1) {
        for (int i = 0; i < n; i++) {
            if (used[i]) continue;
            v.push_back(i);
            used[i] = true;
            dfs(v, used);
            v.pop_back();
            used[i] = false;
        }
    }

    else {
        int i;
        for (int j = 0; j < n; j++) {
            if (!used[j]) {
                i = j;
                break;
            }
        }
        v.push_back(i);
        used[i] = true;
        dfs(v, used);
        v.pop_back();
        used[i] = false;
    }
}


int main() {
    cin >> n;
    for (int i = 0; i < n; i++) cin >> a[i];
    
    vector<int> v;
    vector<bool> used(n, false);
    dfs(v, used);

    cout << ans << endl;
}