Zeromutarts - Serial verifier

Website :  http://zeromutarts.de/

Question :
Try to validate the nice little piece of code. You will get your flag here: Serial verifier

As i tried on windows i would like to share only windows

File : Windows

Solution : 
Click on Serial verifier link.You would get this

I used ida-pro.
Basic approach : view->open subviews->strings , you would land up something like this :-)

Now double clicking on the string "I would like to know your serial now" ,you would landup to ida-view.switch to graph-view and again go to view->open subviews->pseudocode


There you go see the logic used?

Manually calculate or write a similar script to do it faster :-)
Submit the serial with whatever Session-id (1751)

Serial key i got is 280832-3551148-2307
After submiting the serial i get the flag as :
flag{why_so_serial}

FLAG : why_so_serial