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: /* package codechef; // don't place package name! */
  
  import java.util.*;
  import java.lang.*;
  import java.io.*;
  /* Name of the class has to be "Main" only if the class is public. */
  public class Codechef
  {static class FastReader 
      { 
          BufferedReader br; 
          StringTokenizer st; 
    
          public FastReader() 
          { 
              br = new BufferedReader(new
                       InputStreamReader(System.in)); 
          } 
    
          String next() 
          { 
              while (st == null || !st.hasMoreElements()) 
              { 
                  try
                  { 
                      st = new StringTokenizer(br.readLine()); 
                  } 
                  catch (IOException  e) 
                  { 
                      e.printStackTrace(); 
                  } 
              } 
              return st.nextToken(); 
          } 
    
          int nextInt() 
          { 
              return Integer.parseInt(next()); 
          } 
    
          long nextLong() 
          { 
              return Long.parseLong(next()); 
          } 
    
          double nextDouble() 
          { 
              return Double.parseDouble(next()); 
          } 
    
          String nextLine() 
          { 
              String str = ""; 
              try
              { 
                  str = br.readLine(); 
              } 
              catch (IOException e) 
              { 
                  e.printStackTrace(); 
              } 
              return str; 
          } 
      } 
  //    static int mod = 998244353 ;
  //    static int N = 200005;
  //    static long factorial_num_inv[] = new long[N+1];
  //    static long natual_num_inv[] = new long[N+1];
  //    static long fact[] = new long[N+1];
  //    static void InverseofNumber() 
  //{ 
  //    natual_num_inv[0] = 1;
  //    natual_num_inv[1] = 1; 
  //    for (int i = 2; i <= N; i++) 
  //        natual_num_inv[i] = natual_num_inv[mod % i] * (mod - mod / i) % mod; 
  //} 
  //static void InverseofFactorial() 
  //{ 
  //    factorial_num_inv[0] = factorial_num_inv[1] = 1; 
    
  //    for (int i = 2; i <= N; i++) 
  //        factorial_num_inv[i] = (natual_num_inv[i] * factorial_num_inv[i - 1]) % mod; 
  //} 
  //static long nCrModP(long N, long R) 
  //{ 
  //    long ans = ((fact[(int)N] * factorial_num_inv[(int)R]) % mod * factorial_num_inv[(int)(N - R)]) % mod; 
  //    return ans%mod; 
  //}
      //static boolean prime[];
      //static void sieveOfEratosthenes(int n)
      //{
      //    prime = new boolean[n+1];
          
      //    for (int i = 0; i <= n; i++)
      //        prime[i] = true;
   
      //    for (int p = 2; p * p <= n; p++)
      //    {
      //        // If prime[p] is not changed, then it is a
      //        // prime
      //        if (prime[p] == true)
      //        {
      //            // Update all multiples of p
      //            for (int i = p * p; i <= n; i += p)
      //                prime[i] = false;
      //        }
      //    }
   
          
      //}
      
  	public static void main (String[] args) throws java.lang.Exception
  	{
      //    InverseofNumber();
      //    InverseofFactorial();
      //   fact[0] = 1; 
      //   for (long i = 1; i <= 2*100000; i++)
      //   { 
      //       fact[(int)i] = (fact[(int)i - 1] * i) % mod; 
      //   }
      
  		FastReader scan = new FastReader();
  		PrintWriter pw = new PrintWriter(System.out);
          int n = scan.nextInt();
          int arr[] = new int[n];
         int max = Integer.MIN_VALUE;
         for(int i=0;i<n;i++){
             arr[i] = scan.nextInt();
            if(arr[i]>max)
             max = arr[i];
         }
         List<TreeSet<Integer>> a = new ArrayList<TreeSet<Integer>>();
         TreeSet<Integer> ans = new TreeSet<Integer>();
         ans.add(0);
         HashMap<Integer,Integer> hm = new HashMap<>();
         for(int i=0;i<=1024;i++){
             hm.put(i,1024);
         }
         for(int i=0;i<=1024;i++){
             a.add(new TreeSet<Integer>());
         }
         
         for(int i=0;i<n;i++){
             ans.add(arr[i]);
             for(int j=arr[i]+1;j<=hm.get(arr[i]);j++){
              if(a.get(j).contains(arr[i]))
              break;
              else
              a.get(j).add(arr[i]);
             }
             hm.replace(arr[i],Math.min(arr[i],hm.get(arr[i])));
             TreeSet<Integer> temp = a.get(arr[i]);
             for(int ele : temp){
                 int x = ele^arr[i];
                 ans.add(x);
                 for(int j=arr[i]+1;j<=hm.get(x);j++){
                     if(a.get(j).contains(x))
                     break;
                     else
                     a.get(j).add(x);
                 }
                 hm.replace(x,Math.min(arr[i],hm.get(x)));
             }
             temp.clear();
            
         }
         pw.println(ans.size());
         for(int ele : ans){
             pw.print(ele+" ");
         }
         pw.flush();
      }
      
  //   static long gcd(long a,long b){
  //       if(a==0)
  //       return b;
  //       return gcd(b%a,a);
  //   }
  //   static long lcm(long a,long b){
  //       return (a/gcd(a,b))*b;
  //   }
  }
  //class Pair{
  //    Integer x,y;
  //    Pair(int x,int y){
  //        this.x = x;
  //        this.y = y;
  //    }
  //    public boolean equals(Object obj) {
  //        // TODO Auto-generated method stub
  //        if(obj instanceof Pair)
  //        {
  //            Pair temp = (Pair) obj;
  //            if(this.x.equals(temp.x) && this.y.equals(temp.y))
  //                return true;
  //        }
  //        return false;
  //    }
  
  //    @Override
  //    public int hashCode() {
  //        // TODO Auto-generated method stub
          
  //        return (this.x.hashCode() + this.y.hashCode());        
  //    }
  //}
  //class Compar implements Comparator<Pair>{
  //    public int compare(Pair p1,Pair p2){
  //        return p1.x-p2.x;
  //    }
  //}
  