code: def get_c_option_index(args):
      
      try:
          ind_c = args.index('-c')
      except ValueError:
          return -1
      else:
          for i in range(1, ind_c):
              if not args[i].startswith('-'):
                  # there is an arg without "-" before "-c", so it's not an interpreter's option
                  return -1
          return ind_c
docs: Get index of "-c" argument and check if it's interpreter's option
      :param args: list of arguments
      :return: index of "-c" if it's an interpreter's option and -1 if it doesn't exist or program's option