code: def correct_invalid_start(self, scansion: str) -> str:
          
          mark_list = string_utils.mark_list(scansion)
          vals = list(scansion.replace(" ", ""))
          corrected = vals[:2] + [self.constants.STRESSED] + vals[3:]
          new_line = list(" " * len(scansion))
          for idx, car in enumerate(corrected):
              new_line[mark_list[idx]] = car
          return "".join(new_line)
docs: The third syllable of a hendecasyllabic line is long, so we will convert it.
  
          :param scansion: scansion string
          :return: scansion string with corrected start
  
          >>> print(HendecasyllableScanner().correct_invalid_start(
          ... "- U U  U U  - U   -  U - U").strip())
          - U -  U U  - U   -  U - U