#include <iostream>
using namespace std;

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

int main() {
    int N;
    cin >> N;
    for(int i = 0;i < N;i++) cin >> A[i];

    for(int i = 0;i < (1 << N);i++) dp[i] = 0;

    for(int before = 0;before < (1 << N);before++) {
        
        for(int i = 0;i < N;i++) {
            for(int j = 0;j < N;j++) {
                if(!((before >> i) & 1) && !((before >> j) & 1) && i != j) {
                    int after = before;
                    after = after | (1 << i);
                    after = after | (1 << j);
                    dp[after] = std::max(dp[after], dp[before] + (A[i] ^ A[j]));
                }
            }
        }
    }

    cout << dp[(1 << N) - 1] << endl;
}