No, 14! == 87178291200‬ there are two trailing zeros there.

Okay, that was indeed overflow issue. My buffer was initialized as Int. Thanks for quick response!

@sitetester: I already gave you an answer. Ask yourself, why are you returning a negative number? (what makes it happen and how can you avoid it?)

There's 276 scala completions, so it's not an issue with kata itself.

Same issue -1961650628 did not equal 2333316668 for scala

That's not the input, that's your output. So it's you who generated a negative number out of positive numbers ;-)

(Also, as you know, you can always see the input by printing it out.)

Not an issue. You should figure out why yourself ;-)