#include <iostream>
#include <vector>
using namespace std;

int main(){
    int n;
    cin>>n;
    vector<int> a(n);
    for(int i=0;i<n;i++){
        cin>>a[i];
    }

    vector<int> dp(1<<n,0);


    for(int i = 0; i < (1<<n); i++){
        for(int j = 0; j < n; j++){
            if ((i & (1<<j) )!= 0) continue;
            for(int k = 0; k < n; k++){
                if ((i & (1<<k) )!= 0) continue;
                if (j == k) continue ; 
                int new_i= i | (1<<j) | (1<<k);
                dp[new_i] = max(dp[i] + (a[j]^a[k]), dp[new_i]);
            }
        }
    }

    cout <<dp[(1<<n)-1]<<endl;
    return 0;
}