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 math
  import os
  import sys
  from io import BytesIO, IOBase
  M = 1000000007
  import random
  import heapq
  import threading
  import bisect
  import time
  from functools import *
  from collections import *
  from itertools import *
  BUFSIZE = 8192
  import array
  class FastIO(IOBase):
      newlines = 0
      def __init__(self, file):
          self._fd = file.fileno()
          self.buffer = BytesIO()
          self.writable = "x" in file.mode or "r" not in file.mode
          self.write = self.buffer.write if self.writable else None
      def read(self):
          while True:
              b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
              if not b:
                  break
              ptr = self.buffer.tell()
              self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
          self.newlines = 0
          return self.buffer.read()
      def readline(self):
          while self.newlines == 0:
              b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
              self.newlines = b.count(b"\n") + (not b)
              ptr = self.buffer.tell()
              self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
          self.newlines -= 1
          return self.buffer.readline()
      def flush(self):
          if self.writable:
              os.write(self._fd, self.buffer.getvalue())
              self.buffer.truncate(0), self.buffer.seek(0)
  class IOWrapper(IOBase):
      def __init__(self, file):
          self.buffer = FastIO(file)
          self.flush = self.buffer.flush
          self.writable = self.buffer.writable
          self.write = lambda s: self.buffer.write(s.encode("ascii"))
          self.read = lambda: self.buffer.read().decode("ascii")
          self.readline = lambda: self.buffer.readline().decode("ascii")
  def print(*args, **kwargs):
      sep, file = kwargs.pop("sep", " "), kwargs.pop("file", sys.stdout)
      at_start = True
      for x in args:
          if not at_start:
              file.write(sep)
          file.write(str(x))
          at_start = False
      file.write(kwargs.pop("end", "\n"))
      if kwargs.pop("flush", False):
          file.flush()
  if sys.version_info[0] < 3:
      sys.stdin, sys.stdout = FastIO(sys.stdin), FastIO(sys.stdout)
  else:
      sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
  input = lambda: sys.stdin.readline().rstrip("\r\n")
  def inp(): return sys.stdin.readline().rstrip("\r\n")  # for fast input
  def out(var): sys.stdout.write(str(var))  # for fast output, always take string
  def lis(): return list(map(int, inp().split()))
  def stringlis(): return list(map(str, inp().split()))
  def sep(): return map(int, inp().split())
  def strsep(): return map(str, inp().split())
  def fsep(): return map(float, inp().split())
  def inpu(): return int(inp())
  
  def build(arr,a,b,st,node):
      if a==b:
          st[node] =  arr[a]
          return st[node]
      mid = (a+b)//2
      st[node] = min(build(arr,a,mid,st,2*node+1) , build(arr,mid+1,b,st,2*node+2))
      return st[node]
  
  def getmin(arr,a,b,l,r,st,node):
      if l>b or r<a:
          return float("inf")
      if l<=a and r>=b:
          return st[node]
      mid = (a+b)//2
      return min(getmin(arr,a,mid,l,r,st,2*node+1),getmin(arr,mid+1,b,l,r,st,2*node+2))
  
  def chck(x,y,z):
      #print(x[0]*(y[1]-z[1]) + y[0]*(z[1]-x[1]) + z[0]*(x[1]-y[1]))
      if abs(x[0]*(y[1]-z[1]) + y[0]*(z[1]-x[1]) + z[0]*(x[1]-y[1]))>0:
          return True
      return False
  
  
  """def fun(s,res,n):
      l = []
      for i in range(len(s)):
          if s[i] == res:
              l.append(i)
      ans = 0
      d = defaultdict(int)
      for i in l:
          d[i] += 1
      p = []
      for i in l[::-1]:
          if n - 1 - i in d:
              continue
          else:
              #flag = False
              p.append(i)
              ans += 1
              n-=1
      pp = ""
      for i in range(n):
          if len(p) > 0 and i == p[0]:
              p.pop(0)
          else:
              pp += s[i]
      print(pp)
      if pp==pp[::-1]:
          return ans
      else:
          return -1"""
  
  def main():
      t = 1
      #t=inpu()
      for _ in range(t):
          n = inpu()
          arr = lis()
          dp = [10**18]*(513)
          dp[0]=0
          for i in range(n):
              for j in range(513):
                  if dp[j]<arr[i]:
                      dp[j^arr[i]] = min(dp[j^arr[i]],arr[i])
          ans=[]
          for i in range(513):
              if dp[i]!=10**18:
                  ans.append(i)
          print(len(ans))
          print(*ans)
  if __name__ == '__main__':
      """
      threading.stack_size(2*10**8)
      threading.Thread(target=main).start()
      """
      main()
  