#include "bits/stdc++.h"
#define REP(i,n,N) for(ll i=(n); i<(N); i++)
#define RREP(i,n,N) for(ll i=(N-1); i>=n; i--)
#define CK(n,a,b) ((a)<=(n)&&(n)<(b))
#define ALL(v) (v).begin(),(v).end()
#define p(s) cout<<(s)<<endl
#define p2(a,b) cout<<(a)<<" "<<(b)<<endl
#define v2(T) vector<vector<T>>
typedef long long ll;
using namespace std;
const int INF = 1e9;
const int MOD = 1e9+7;
const ll LLINF = 1e18;

ll dp[1<<14];
vector<ll> A(15);
int main(){
    int N;
    cin>>N;
    REP(i,0,N){
        cin>>A[i];
    }
    REP(mask,0,1<<N){
        REP(i,0,N){
            if(mask & (1<<i)) continue;
            REP(j,i+1,N){
                if(mask & (1<<j)) continue;
                dp[mask|(1<<i)|(1<<j)] = max(dp[mask|(1<<i)|(1<<j)], dp[mask]+(A[i]^A[j]));
            }
        }
    }
    p(dp[(1<<N)-1]);
    return 0;
}