#include<bits/stdc++.h>
typedef long long ll;
using namespace std;
const ll MOD = 1e9+7;
const ll MAX= 1000001;
int main(){
	int n;
	cin>>n;
	int a[n];
	int dp[1<<14];
	for(int i=0; i<n; i++){
		cin>>a[i];
	}
	for(int mask=0; mask<(1<<n); mask++){
		for(int i=0; i<n; i++){
			for(int j=i+1; j<n; j++){
				if(mask&(1<<i)||mask&(1<<j)){
					continue;
				}
				dp[mask+(1<<i)+(1<<j)]=max(dp[mask+(1<<i)+(1<<j)],dp[mask]+(a[i]^a[j]));
			}
		}
	}
	cout<<dp[(1<<n)-1]<<endl;
}