Delta_G:
Actually, I think what you posted gives 20, which is larger than he needs so it doesn't end up with any memory being stomped on and it will "work" in his code. But it isn't the right answer. Could write a test code if you'd like.
No need, I rechecked the little test I'd written and saw a critical error. Cause: Inattention to detail. Mea culpa! 
I think my next project needs to be a mind-reading compiler.