description: This is an easier version of the problem with smaller constraints.
  
  Korney Korneevich dag up an array a of length n. Korney Korneevich has recently read about the operation [bitwise XOR](https://en.wikipedia.org/wiki/Bitwise_operation#XOR), so he wished to experiment with it. For this purpose, he decided to find all integers x ≥ 0 such that there exists an increasing subsequence of the array a, in which the bitwise XOR of numbers is equal to x.
  
  It didn't take a long time for Korney Korneevich to find all such x, and he wants to check his result. That's why he asked you to solve this problem!
  
  A sequence s is a subsequence of a sequence b if s can be obtained from b by deletion of several (possibly, zero or all) elements.
  
  A sequence s_1, s_2, … , s_m is called increasing if s_1 < s_2 < … < s_m.
  
  Input
  
  The first line contains a single integer n (1 ≤ n ≤ 10^5).
  
  The second line contains n integers a_1, a_2, …, a_n (0 ≤ a_i ≤ 500) — the elements of the array a.
  
  Output
  
  In the first line print a single integer k — the number of found x values.
  
  In the second line print k integers in increasing order x_1, x_2, … x_k (0 ≤ x_1 < … < x_k) — found x values.
  
  Examples
  
  Input
  
  
  4
  4 2 2 4
  
  
  Output
  
  
  4
  0 2 4 6 
  
  
  Input
  
  
  8
  1 0 1 7 12 5 3 2
  
  
  Output
  
  
  12
  0 1 2 3 4 5 6 7 10 11 12 13 
  
  Note
  
  In the first test case:
  
    * To get value x = 0 it is possible to choose and empty subsequence 
    * To get value x = 2 it is possible to choose a subsequence [2] 
    * To get value x = 4 it is possible to choose a subsequence [4] 
    * To get value x = 6 it is possible to choose a subsequence [2, 4] 
solution: import java.io.*;
  import java.util.*;
  
  public class codeforces_750_F1 {
      private static void solve(FastIOAdapter io) {
          int n = io.nextInt();
          int[] a = io.readArray(n);
  
          int maxVal = 1 << 13;
          boolean[] ans = new boolean[maxVal];
          ArrayList<ArrayList<Integer>> g = new ArrayList<>();
          int[] r = new int[maxVal];
  
          ans[0] = true;
          for (int i = 0; i < maxVal; i++) {
              ArrayList<Integer> cur = new ArrayList<>();
              cur.add(0);
              g.add(cur);
          }
          Arrays.fill(r, maxVal - 1);
  
          for (int i = 0; i < n; i++) {
              ArrayList<Integer> list = g.get(a[i]);
              for (Integer num : list) {
                  int res = num ^ a[i];
                  ans[res] = true;
                  while (r[res] > a[i]) {
                      g.get(r[res]).add(res);
                      r[res]--;
                  }
              }
              list.clear();
          }
          int count = 0;
          for (int i = 0; i < ans.length; i++) {
              if (ans[i]) {
                  count++;
              }
          }
          io.out.println(count);
          for (int i = 0; i < ans.length; i++) {
              if (ans[i]) {
                  io.out.print(i + " ");
              }
          }
          io.out.println();
      }
  
      public static void main(String[] args) throws Exception {
          try (FastIOAdapter ioAdapter = new FastIOAdapter()) {
              int count = 1;
              //count = ioAdapter.nextInt();
              while (count-- > 0) {
                  solve(ioAdapter);
              }
          }
      }
  
      static void ruffleSort(int[] arr) {
          int n = arr.length;
          Random rnd = new Random();
          for (int i = 0; i < n; ++i) {
              int tmp = arr[i];
              int randomPos = i + rnd.nextInt(n - i);
              arr[i] = arr[randomPos];
              arr[randomPos] = tmp;
          }
          Arrays.sort(arr);
      }
  
      static void ruffleSort(long[] arr) {
          int n = arr.length;
          Random rnd = new Random();
          for (int i = 0; i < n; ++i) {
              long tmp = arr[i];
              int randomPos = i + rnd.nextInt(n - i);
              arr[i] = arr[randomPos];
              arr[randomPos] = tmp;
          }
          Arrays.sort(arr);
      }
  
      static class FastIOAdapter implements AutoCloseable {
          BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
          public PrintWriter out = new PrintWriter(new BufferedWriter(new OutputStreamWriter((System.out))));
          StringTokenizer st = new StringTokenizer("");
  
          String next() {
              while (!st.hasMoreTokens())
                  try {
                      st = new StringTokenizer(br.readLine());
                  } catch (IOException e) {
                      e.printStackTrace();
                  }
              return st.nextToken();
          }
  
          String nextLine() {
              try {
                  return br.readLine();
              } catch (IOException e) {
                  e.printStackTrace();
                  return null;
              }
          }
  
          int nextInt() {
              return Integer.parseInt(next());
          }
  
          int[] readArray(int n) {
              int[] a = new int[n];
              for (int i = 0; i < n; i++) a[i] = nextInt();
              return a;
          }
  
          long[] readArrayLong(int n) {
              long[] a = new long[n];
              for (int i = 0; i < n; i++) a[i] = nextLong();
              return a;
          }
  
          long nextLong() {
              return Long.parseLong(next());
          }
  
          @Override
          public void close() throws Exception {
              out.flush();
              out.close();
              br.close();
          }
      }
  }
  