#include <bits/stdc++.h>
typedef unsigned long long ll;
#define INF 1000000000
using namespace std;
int main(void){
    int n;
    cin>>n;
    vector<int>A(n);
    for(int i=0;i<n;i++){
        cin>>A[i];
    }
    int dp[1<<14]={-1};
    dp[0]=0;
    for(int mask=0;mask<(1<<n);mask++){
        for(int a=0;a<n;a++){
            for(int b=0;b<n;b++){
                if (a == b or (mask >> a) & 1 or (mask >> b) & 1)
                {
                    continue;
                }
                int nextMask = mask | (1 << a) | (1 << b);
                dp[nextMask] = max(dp[nextMask], dp[mask] + (A[a] ^ A[b]));
            }
        }
    }
    cout<<dp[(1<<n)-1]<<endl;
 
}