Very clever

gg man

one liners in python aren't always exactly "elegant". but yes

Cool!

I didn't think this way, thanks for sharing

The solution in C, C++ and other languages takes at least 5 lines. An elegant solution in Python is always:

Oh! If only I'd actually written the math down on a piece of paper.
That is so elegant :)

woah... that's why maths is fantastic

thank you, sir.

was confused at first....damn !

awesome.while len(arr) == 1 , it will calculate normally to be 0.

Awesome! This is brain wave! Clear mathematical point of view. I've tendency to solve such tasks rather directly.

Could you elaborate for us slower types, please?

Nice!

I don't get it :|