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