def exchange_maskint(mask_int):
 bin_arr = ['0' for i in range(32)]
 for i in range(mask_int):
 bin_arr[i] = '1'
 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)