#include <bits/stdc++.h>
// #include <atcoder/all>
// using namespace atcoder;
#define rep(i, n) for (int i = 0; i < (n); i++)
using ll = long long;
using namespace std;
const int mod = 1000000007;
const int INF =1e9+1;
int main(){
  int n;cin>>n;
  vector<int> a(n);
  rep(i,n)cin>>a[i];
  int n2=1<<n;
  vector<int> dp(n2);
  rep(i,n2){
    rep(j,n){
      if(i>>j&1)continue;
      for(int k=j+1;k<n;k++){
        if(i>>k&1)continue;
        int x=1<<j|1<<k;
        x=i|x;
        dp[i|(1<<j)|(1<<k)]=max(dp[i|(1<<j)|(1<<k)],dp[i]+(a[j]^a[k]));
      }
    }
  }
  cout<<dp[n2-1]<<endl;
}