input: from typing import List
  
  def first_non_repeating_char(lst: List[int]) -> int:
      """
      Finds the first non-repeating character in a given list.
      >>> first_non_repeating_char([1, 2, 3, 4, 4, 3, 2, 1])
      6
      """
output:     count = {}
      for num in lst:
          if num in count:
              count[num] += 1
          else:
              count[num] = 1
      for i, num in enumerate(lst):
          if count[num] == 1:
              return i
      return -1