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.*;
  import java.io.*;
  public class Main {
  		static long mod = 1000000007;
  		static long max ;
  		static PrintWriter out = new PrintWriter(new BufferedOutputStream(System.out));
  		public static void main(String[] args) throws IOException  {
  			FastReader sc = new FastReader();
  			int n = sc.nextInt();
  			int arr[] = new int[n];
  			for( int i = 0 ;i < n; i++) {
  				arr[i] = sc.nextInt();
  			}
  			int dp[] = new int[516];
  			for( int i= 0 ;i < 516 ; i++) {
  				dp[i] = Integer.MAX_VALUE;
  			}
  			dp[0] = 0;
  			for( int i = 0 ;i < n ;i++) {
  				for( int j = 0 ; j < 516 ; j++) {
  					if( arr[i] > dp[j]) {
  						dp[j^arr[i]] = Math.min(dp[j^arr[i]], arr[i]);
  					}
  				}
  			}
  			long count = 0;
  			ArrayList<Integer> x = new ArrayList<>();
  			for( int i= 0 ; i< 516 ; i++) {
  				if( dp[i] < Integer.MAX_VALUE) {
  					count++;
  					x.add(i);
  				}
  			}
  			out.println(count);
  			for( int y : x) {
  				out.print(y + " ");
  			}
  			out.println();
  			out.flush();
  		}
  	
  		public static boolean ifpowof2(long n ) {
  			return ((n&(n-1)) == 0);
  		}
  		
  		public static int[] nextLargerElement(int[] arr, int n)	{ 
  			Stack<Integer> stack = new Stack<>();
  			int rtrn[] = new int[n];
  			rtrn[n-1] = -1;
  	        stack.push( n-1);
  	        for( int i = n-2 ;i >= 0 ; i--){
  	            int temp = arr[i];
  	            int lol = -1;
  	            while( !stack.isEmpty() && arr[stack.peek()] <= temp){
  	            	if(arr[stack.peek()] == temp ) {
  	            		lol = stack.peek();
  	            	}
  	                stack.pop();
  	            }
  	            if( stack.isEmpty()){
  	            	if( lol != -1) {
  	            		rtrn[i] = lol;
  	            	}
  	            	else {
  	            		rtrn[i] = -1;
  	            	}
  	            }
  	            else{
  	            	rtrn[i] = stack.peek();
  	            }
  	            stack.push( i);
  	        }
  	        return rtrn;
  		}
  		
  		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;
  		 }
  		 
  
  		 static long rightmostsetbit(long n) {
  			 return n&-n;
  		 }
  		 
  		 static long leftmostsetbit(long n)
  		    {
  		        long k = (long)(Math.log(n) / Math.log(2));
  		        return 1 << k;
  		    }
  	 
  		 static HashMap<Long,Long> primefactor( long n){
  			 HashMap<Long ,Long> hm = new HashMap<>();
  			 long temp = 0;
  			 while( n%2 == 0) {
  				 temp++;
  				 n/=2;
  			 }	
  			 if( temp!= 0) {
  				 hm.put( 2L, temp);
  			 }
  			 long c = (long)Math.sqrt(n);
  			 for( long i = 3 ; i <= c ; i+=2) {
  				 temp = 0;
  				 while( n% i == 0) {
  					 temp++;
  					 n/=i;
  				 }
  				 if( temp!= 0) {
  					 hm.put( i, temp);
  				 }
  	 		 }
  	 		 if( n!= 1) {
  	 			 hm.put( n , 1L);
  	 		 }
  	 		 return hm;	
  		 }
  		 
  		 @SuppressWarnings("unused")
  		private static ArrayList<Integer> allfactors(int abs) {
  			 HashMap<Integer,Integer> hm = new HashMap<>();
  			 ArrayList<Integer> rtrn = new ArrayList<>();
  			 for( int i = 2 ;i*i <= abs; i++) {
  				 if( abs% i == 0) {
  					 hm.put( i , 0);
  					 hm.put(abs/i, 0);
  				 }
  			 }
  			 for( int x : hm.keySet()) {
  				 rtrn.add(x);
  			 }
  			 
  			 if( abs != 0) {
  				 rtrn.add(abs);
  			 }
  			 
  			 return rtrn;
  		 }
  			
  	 
  		 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;
  			 }
  		 }	
  }