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.util.ArrayList;
  import java.util.Arrays;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.HashSet;
  import java.util.LinkedList;
  import java.util.List;
  import java.util.PriorityQueue;
  import java.util.Queue;
  import java.util.StringTokenizer;
  
  
  import java.io.*;
   
  public class cf745 {
  	
  	private static class MyScanner {
  	    BufferedReader br;
  	    StringTokenizer st;
   
  	    public MyScanner() {
  	       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;
  	    }
   
  	 }
  
  	public static void solution(int n, int[] arr)	
  	{
  		int[] ans = new int[512];
  		for(int i = 0 ;i<512; i++)
  			ans[i] = -1;
  		
  		for(int i = n-1; i>=0; i--)
  		{
  			int curr = arr[i];
  			ans[curr] = Math.max(ans[curr], curr);
  			
  			for(int j = 0; j<512; j++)
  			{
  			   if(ans[j]>curr)
  				   ans[j^curr] = Math.max(ans[j^curr], curr);
  			}
  		}
  		
  		ans[0] = 1;
  		int count = 0;
  		
  		for(int i = 0; i<512; i++)
  			{
  			    if(ans[i]>=0)
  			    	count++;
  			}
  		
  		out.println(count);
  		
  		for(int i = 0; i<512; i++)
  			{
  			    if(ans[i]>=0)
  			      out.print(i+" ");
  			}
  		
  	}
  	
  	
  private static PrintWriter out = new PrintWriter(System.out);
   
  public static void main (String[] args)
  {
  	MyScanner s =  new MyScanner();
      
  	int n = s.nextInt();
  		int[] arr = new int[n];
  		
  		for(int i = 0; i<n; i++)
  			arr[i] = s.nextInt();
   		
          solution(n,arr);
      
       
      out.flush();
      out.close();
  }
  }