import java.io.*;
import java.util.*;

public class Main {
    static int n;
    static int[] values;
    static int max = 0;
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        n = sc.nextInt();
        values = new int[n];
        for (int i = 0; i < n; i++) {
            values[i] = sc.nextInt();
        }
        calc(0, new boolean[n], 0);
        System.out.println(max);
    }
    
    static void calc(int idx, boolean[] used, int v) {
        if (idx >= n) {
            max = Math.max(max, v);
        }
        for (int i = 0; i < n; i++) {
            if (used[i]) {
                continue;
            }
            used[i] = true;
            for (int j = i + 1; j < n; j++) {
                if (used[j]) {
                    continue;
                }
                used[j] = true;
                calc(idx + 2, used, v ^ (values[i] + values[j]));
                used[j] = false;
            }
            used[i] = false;
            break;
        }
    }
    
}

class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public String next() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
}