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

int N, A[19];

int dfs(int flg, int val = 0){
    int i = __builtin_ctz(~flg);
    if (i == N) return val;
    flg |= 1<<i;
    int best = 0;
    
    int j = __builtin_ctz(~flg), b = ~flg;
    while (j < N){
        best = max(best, dfs(flg|(1<<j), val^(A[i]+A[j])));
        j = __builtin_ctz(b ^= 1<<j);
    }
    return best;
}

int main(){
    cin >> N;
    for (int i=0; i<N; ++i) cin>>A[i];
    cout << dfs(0) << endl;
    return 0;
}