Problems from 2021 ICPC North America Division Championships

	Submissions				Users
Name	Total	Acc.	Ratio	Fastest	Total	Acc.	Ratio	Difficulty
Alien Microwave	236	94	40%	0.00	123	90	73%	6.5
Another Substring Query Problem	785	143	18%	0.18	197	83	42%	8.3
Borders	346	85	25%	0.00	115	74	64%	7.4
Circle of Friends	163	50	31%	0.15	44	32	73%	6.8
Finding Polly	166	52	31%	0.66	22	16	73%	6.6
Investigating Imposters	465	175	38%	0.00	211	152	72%	6.0
Laptop Sticker	1434	931	65%	0.00	898	872	97%	1.4
Longest Common Substring	749	224	30%	0.00	249	189	76%	4.6
Simple Cron Spec	400	254	64%	0.01	255	238	93%	1.9
Surveillance	84	27	32%	0.00	22	16	73%	6.3
Train Line	176	32	18%	0.57	31	19	61%	8.5
Window Shopping	26	10	38%	0.10	14	9	64%	7.6
You Be the Judge!	1044	197	19%	0.00	255	179	70%	5.4