I think it that particular case they just didn't do error analysis. The task was to output answer with `10^-6` precision, which they solution didn't achieve. F

I think it that particular case they just didn't do error analysis. The task was to output answer with `10^-6` precision, which they solution didn't achieve. Funnily enough the number of other teams went the "correct" route and passed (as they were doing additions in same order as original solution).