code: '''simple docstring'''
  
  
  
  
  
  def 				__lowercase	(						lowerCamelCase__					)				->int:
  
    '''simple docstring'''
  
  
  
  
    barcode //= 10  # exclude the last digit
    a__     		=     False
    a__     		=     0
  
    # extract and check each digit
    while barcode != 0:
      a__     		=     1 if checker else 3
      s += mult * (barcode % 10)
      barcode //= 10
      a__     		=     not checker
  
    return (10 - (s % 10)) % 10
  def 				__lowercase	(						lowerCamelCase__					)				->bool:
  
    '''simple docstring'''
  
  
  
  
    return len(str(UpperCAmelCase_					)					) == 13 and get_check_digit(UpperCAmelCase_					) == barcode % 10
  def 				__lowercase	(						lowerCamelCase__					)				->int:
  
    '''simple docstring'''
  
  
  
  
    if str(UpperCAmelCase_					).isalpha():
      a__     		=     f"Barcode \'{barcode}\' has alphabetic characters."
      raise ValueError(UpperCAmelCase_					)
    elif int(UpperCAmelCase_					) < 0:
      raise ValueError("The entered barcode has a negative value. Try again."					)
    else:
      return int(UpperCAmelCase_					)
  
  
  if __name__ == "__main__":
       import doctest
  
       doctest.testmod()
       _SCREAMING_SNAKE_CASE   						=    get_barcode(input("""Barcode: """).strip())
  
       if is_valid(barcode):
            print(F"""'{barcode}' is a valid barcode.""")
       else:
            print(F"""'{barcode}' is NOT a valid barcode.""")
  
  
style_context: def 				__lowercase	(						lowerCamelCase__ ,				lowerCamelCase__					)				->Optional[int]:
  
    '''simple docstring'''
  
  
  
  
    sequence.append(lowerCamelCase__					)
  
    a__     		=     0
    while sequence[index] != target:
      index += 1
  
    sequence.pop()
  
    if index == len(lowerCamelCase__					):
      return None
  
    return index
  
  
  if __name__ == "__main__":
       _SCREAMING_SNAKE_CASE   						=    input("""Enter numbers separated by comma:\n""").strip()
       _SCREAMING_SNAKE_CASE   						=    [int(item) for item in user_input.split(""",""")]
  
       _SCREAMING_SNAKE_CASE   						=    input("""Enter a single number to be found in the list:\n""")
       _SCREAMING_SNAKE_CASE   						=    int(target_input)
       _SCREAMING_SNAKE_CASE   						=    sentinel_linear_search(sequence, target)
       if result is not None:
            print(F"""{target} found at positions: {result}""")
       else:
            print("""Not found""")
  
  