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

int main(){
    int n;
    cin>>n;
    vector<ll> a(n);
    for(int i = 0;i<n;i++) cin>>a[i];
    vector<ll> dp(1<<n,0);
    for(int i = 0;i<1<<n;i++){
        for(int j = 0;j<n;j++) if(~i>>j&1) {
            for(int k = j + 1;k<n;k++) if(~i>>k&1) {
                dp[i|1<<j|1<<k] = max(dp[i|1<<j|1<<k],dp[i]+(a[j]^a[k]));
            }
        }
    }
    cout<<dp[(1<<n)-1]<<endl;
    //for(int i = 0;i<1<<n;i++) cout<<dp[i]<<" ";
}