#include "bits/stdc++.h"
#define ALL(obj) (obj).begin(),(obj).end()
#define RALL(obj) (obj).rbegin(),(obj).rend()
#define REP(i, n) for(int i = 0; i < (int)(n); i++)
#define REPR(i, n) for(int i = (int)(n); i >= 0; i--)
#define FOR(i,n,m) for(int i = (int)(n); i < int(m); i++)
using namespace std;
typedef long long ll;
const int MOD = 1e9 + 7;
const int INF = MOD - 1;
const ll LLINF = 4e18;

int main() {
    int n; cin >> n;
    vector<int> a(n);
    REP(i, n)  cin >> a[i];
    int ans = 0;
    do {
        int s = 0;
        REP(i, n / 2) {
            s ^= a[i] + a[i + n / 2];
        }
        ans = max(ans, s);
        reverse(a.begin() + n / 2, a.end());
    } while (next_permutation(ALL(a)));
    cout << ans << endl;
    getchar(); getchar();
}