def exchange_maskint(mask_int):

  bin_arr = ['' for i in range(32)]

  for i in range(mask_int):

    bin_arr[i] = ''

  tmpmask = [''.join(bin_arr[i * 8:i * 8 + 8]) for i in range(4)]

  tmpmask = [str(int(tmpstr, 2)) for tmpstr in tmpmask]

  return '.'.join(tmpmask)

if __name__ == '__main__':

  print exchange_maskint(24)

exchange_mask = lambda mask: sum(bin(int(i)).count('') \

                                 for i in mask.split('.'))

print(exchange_mask('255.255.0.0'))