For those of us who aren't familiar with the Euclidean algorithm, getting the job done efficiently is clever enough. As for the more acceptable way, I don't recall learning that shortcut in school, but here it is... could have saved me trouble many a time during programming puzzles.

It's always time to learn some regex, but familiarity with str's methods can handle this one simply as well.

I was happy to see someone take the same succinct approach, and then I see you one-upped me with the variable arguments.

Ahh, the default case was the icing on top.

I'm just happy that I was able to factor all this out and come up with the right solution on the first try. I've been out of math class for a while.

But you found it. Don't kick yourself too hard. Computers aren't only used when you know the full formula. They're also used to discover formulas, work around the unknowns, or bypass the tedium. In this case, you didn't readily know the formula but were still able to solve the problem.