Thanks a lot dinglemouse! Now I understand. This is really useful experience for me! Can I ask you if I'll have some quiestions in programming?

So you mean. I don't need to return the value, cause input value had been already changed in the body of the method and in fact I can operate with it without return. Right?
I want to easily place method with return into input parameters of the other method.
Tell me your opinion and make some suggestions to me please. Thanks!

Thanks for your note. I really mix up the example and main test cases.