input: 
  def first_non_repeating_char(lst):
      """ Find the first non-repeating character in the given list.
      >>> first_non_repeating_char([1, 2, 3, 4, 4, 3, 2, 1])
      None
      >>> first_non_repeating_char([5, 6, 5, 6, 7, 8, 7])
      8
      """
  
output:     char_count = {}
      for char in lst:
          if char in char_count:
              char_count[char] += 1
          else:
              char_count[char] = 1
      
      for char in lst:
          if char_count[char] == 1:
              return char
      
      return None