Oh,My God, It takes me two days and about 70 lines to solve this, and yours,still one line. More

I know writing 'ab~~yz' in python code is a bad idea, but I can't find the solution.And I know you must have the solution. More

Congratulations,You get level 20! More

How about [this](http://www.checkio.org/mission/pawn-brotherhood/publications/xiaozhan/python-3/int-with-base18/?ordering=newest)! More

Mine [here](http://www.checkio.org/mission/house-password/publications/xiaozhan/python-3/first/). More

About "Finite state machine",I usually use it in hardware debugging. The data flow comes from hardware(such as serial port) continuously, it's consisted of frames, and the frame structure like this: [head ,length, type, data_1...data_n,check,end] So the data I first receive is like this: [head More