Problems from 2021 ICPC North America Division Championships

	Submissions				Users
Name	Total	Acc.	Ratio	Fastest	Total	Acc.	Ratio	Difficulty
Alien Microwave	243	98	40%	0.00	127	94	74%	6.5
Another Substring Query Problem	830	168	20%	0.18	207	92	44%	8.2
Borders	370	95	26%	0.00	127	82	65%	7.4
Circle of Friends	167	52	31%	0.15	46	34	74%	6.4
Finding Polly	166	52	31%	0.66	22	16	73%	6.7
Investigating Imposters	683	218	32%	0.00	244	170	70%	6.4
Laptop Sticker	2281	1406	62%	0.00	1326	1282	97%	1.4
Longest Common Substring	879	277	32%	0.00	278	211	76%	4.8
Simple Cron Spec	528	318	60%	0.00	299	271	91%	2.0
Surveillance	94	29	31%	0.00	24	18	75%	6.4
Train Line	210	34	16%	0.57	35	21	60%	8.7
Window Shopping	26	10	38%	0.10	14	9	64%	7.6
You Be the Judge!	1211	246	20%	0.00	288	201	70%	5.8