#include <bits/stdc++.h>
using namespace std;

int main(){
    int N;
    cin >> N;
    vector<int> A(N);
    for (int& x : A) cin >> x;

    int ans = 0;
    auto dfs = [&](auto&& self, unsigned int bit, int val) -> void{
        if (bit == (1<<N)-1){
            ans = max(ans, val);
            return;
        }
        int i = (bit);
        for (int j = i+1; j < N; j++){
            if (bit>>j&1) continue;
            self(self, bit|(1<<i)|(1<<j), val^(A[i]+A[j]));
        }
    };

    dfs(dfs, 0, 0);
    cout << ans << endl;
}