import java.io.*; import java.util.*; import java.util.stream.*; public class Main { public static void main(String[] args) throws Exception { Scanner sc = new Scanner(); int n = sc.nextInt(); int[] values = new int[n]; for (int i = 0; i < n; i++) { values[i] = sc.nextInt(); } ArrayList> dp = new ArrayList<>(); dp.add(new TreeSet<>()); dp.get(0).add(0); for (int i = 1; i < (1 << n); i++) { dp.add(new TreeSet<>()); int pop = getPop(i); if (pop % 2 == 1) { continue; } for (int j = 0; j < n; j++) { if ((i & (1 << j)) == 0) { continue; } for (int k = j + 1; k < n; k++) { if ((i & (1 << k)) == 0) { continue; } for (int x : dp.get(i ^ (1 << j) ^ (1 << k))) { dp.get(i).add(x ^ (values[j] + values[k])); } } break; } } System.out.println(dp.get((1 << n) - 1).last()); } static int getPop(int x) { int pop = 0; while (x > 0) { pop += x % 2; x >>= 1; } return pop; } } 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(); } }