#include<iostream>
#include<algorithm>
#include<utility>
#include<vector>
#include<cmath>
using namespace std;

typedef pair<int, int> P;
typedef long long ll;
const int INF = 100000000;

ll gcd( ll a, ll b ){//最大公約数
    ll tmp;
    if( a < b ) { tmp = a; a = b; b = tmp; }
    if( b < 1 ) return -1;

    if( a % b == 0 ) return b;
    return gcd( b, a % b );
}

ll lcm(ll a, ll b){//最小公倍数
    return a * b / gcd(a, b);
}


//入力
int n;
int a[20];

int dp[1<<14];

int main(){

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

    for(int before = 0; before < (1 << n); before++){
        for(int i = 0; i < n; i++){
            for(int j = 0; j < n; j++){
                if(i == j) continue;
                if(before & (1 << i) || before & (1 << j)) continue;

                int after = before;
                after |= (1 << i);
                after |= (1 << j);

                dp[after] = max(dp[after], dp[before] + (a[i] ^ a[j]));
            }
        }
    }

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

    return 0;
}