#include <iostream>
#include <algorithm>
#include <vector>
#include <string>
#include <cstring>
#include <complex>
#include <stack>
#include <queue>
#include <unordered_map>
#include <map>
#define INF 100000000
#define rep(i, a) for (int i = 0; i < (a); i++)
using namespace std;
int main() {
    int n;
    cin >> n;
    int dp[1<<n];
    int p[n];
    for(int i=0;i<(1<<n);i++) {
        dp[i] = 0;
    }
    for(int i=0;i<n;i++) {
        cin >> p[i];
    }

    for(int i=0;i<(1<<n);i++) {
        for(int j=0;j<n;j++) {
            for(int k=0;k<n;k++) {
                if(k==j) continue;
                if((i>>k)%2 == 1 || (i>>j)%2 == 1) continue;
                
                int nexti = i | (1<<k) | (1<<j);
                int nextd = dp[i] + (p[j]^p[k]);
                dp[nexti] = max(dp[nexti], nextd);
            }
        }
    }
    cout << dp[(1<<n)-1] << endl;
}