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

public class Main {
    static int[] values;
    static int ans = 0;
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int n = sc.nextInt();
        values = new int[n];
        for (int i = 0; i < n; i++) {
            values[i] = sc.nextInt();
        }
        check(n, new boolean[n], 0);
        System.out.println(ans);
    }
    
    static void check(int idx, boolean[] used, int current) {
        if (idx == 0) {
            ans = Math.max(current, ans);
            return;
        }
        for (int i = 0; i < used.length; i++) {
            if (used[i]) {
                continue;
            }
            used[i] = true;
            for (int j = i + 1; j < used.length; j++) {
                if (used[j]) {
                    continue;
                }
                used[j] = true;
                check(idx - 2, used, current ^ (values[i] + values[j]));
                used[j] = false;
            }
            used[i] = false;
            break;
        }
    }
}
class Utilities {
    static String arrayToLineString(Object[] arr) {
        return Arrays.stream(arr).map(x -> x.toString()).collect(Collectors.joining("\n"));
    }
    
    static String arrayToLineString(int[] arr) {
        return String.join("\n", Arrays.stream(arr).mapToObj(String::valueOf).toArray(String[]::new));
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    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 int[] nextIntArray() throws Exception {
        return Stream.of(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray();
    }
    
    public String next() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
    
}