#include <bits/stdc++.h>
using namespace std;
#define i64 long long
#define rep(i,s,e) for(int (i) = (s);(i) <= (e);(i)++)

int N;
vector<i64> A;
i64 ans = 0;
int rec(int bit,i64 XOR){
    if(bit == (1 << N) - 1){
        ans = max(ans , XOR);
        return 0;
    }
    for(int i = 0;i < N;i++){
        for(int j = 0;j < N;j++){
            if(i == j) continue;
            if((bit & (1<< i))) continue;
            if((bit & (1<< j))) continue;
            rec(bit | (1 << i) | (1 << j) , XOR ^ (A[i] + A[j]));
        }
    }
    return 0;
}
int main(){
    cin >> N;
    A.resize(N);
    rep(i,0,N - 1) cin >> A[i];
    rec(0,0);
    cout << ans << endl;
}