import re


def get_imsi(line):
    """get the correct 15 digits IMSI from the raw IMSI string:
    example:
      input 'line':
        64009778311904f1
      return:
        460079871391401
    """
    couple_chars = re.findall(r'.{2}', line)
    return ''.join([c[::-1] for c in couple_chars])[:-1]