#include<iostream>
#include<algorithm>
using namespace std;
int dp[1<<14];
int n,a[14];
main()
{
	cin>>n;
	for(int i=0;i<n;i++)cin>>a[i];
	for(int i=0;i<1<<n;i++)
	{
		if(__builtin_popcount(i)%2)continue;
		for(int j=0;j<n;j++)
		{
			if(i&1<<j)continue;
			for(int k=0;k<n;k++)
			{
				if(i&1<<k)continue;
				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;
}