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

int n;
int dp[1<<14];
int A[14];

void dfs(int bit)
{
	for(int i = 0;i<n;i++)
	{
		for(int j = i+1;j<n;j++)
		{
			if(((bit&(1<<i))==0)&&((bit&(1<<j))==0))
			{
				//cout<<';'<<endl;
				if(dp[bit]+(A[i]^A[j])>dp[bit+(1<<i)+(1<<j)])
				{
					dp[bit+(1<<i)+(1<<j)] = dp[bit] + (A[i]^A[j]);
					dfs(bit+(1<<i)+(1<<j));
				}
			}
		}
	}
}

int main()
{
	cin >> n;
	for(int i = 0 ;i<n;i++)cin >> A[i];
	dfs(0);
	//for(int i = 0; i<(1<<n);i++)cout<<dp[i]<<endl;
	cout<<dp[(1<<n)-1]<<endl;
	return 0;
}