Problem A
Blackboard Numbers — Problem Statistics

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Submissions	2883
Accepted submissions	806
Submission ratio	27.96%
Authors	675
Full solves [?]	572
Full solve Ratio	84.74%

#	User	Runtime	Language	Date
1	Daniel Worsnup	0.02 s	C	2016-05-01 06:47:18
2	Isaac Saffold	0.02 s	C	2018-12-25 01:36:32
3	Eyleifur Bjarkason	0.03 s	C	2019-03-15 18:05:39
4	David Hinschberger	0.04 s	C	2018-04-11 00:25:59
5	Tandin Wangchuk	0.04 s	C	2019-06-02 16:10:10
6	Ivan Petrov	0.04 s	C	2019-11-11 09:21:56
7	Marko Grabas	0.04 s	C	2019-11-16 16:47:53
8	i_love_ pickles	0.04 s	C	2019-11-26 16:06:11
9	Bianca Benedictos	0.04 s	C	2019-12-17 19:15:20
10	Maria Jose Elumba	0.04 s	C	2019-12-18 08:27:47

#	User	Runtime	Language	Date
1	Gustav Kalander	0.04 s	C#	2018-06-11 19:43:06
2	Thang Le Huu	0.05 s	C#	2019-11-28 06:09:37
3	Kelvin Snepvangers	0.06 s	C#	2018-10-06 22:47:32
4	Sjoerd Teunisse	0.06 s	C#	2018-10-06 22:48:17
5	Mike Garrett	0.06 s	C#	2019-03-04 05:16:21

#	User	Runtime	Language	Date
1	Noah Weninger	0.00 s	C++	2018-12-25 06:53:21
2	Magnus Hegdahl	0.00 s	C++	2022-01-06 21:26:28
3	Frederick Ivan Tan	0.00 s	C++	2023-02-18 08:38:29
4	Max Nilsson	0.00 s	C++	2023-09-13 01:15:38
5	Gao Tianrun	0.00 s	C++	2024-03-28 08:22:39
6	Tan Kwang Thiag	0.00 s	C++	2024-03-31 21:28:42
7	Trần Cảnh Nam	0.00 s	C++	2025-03-02 15:43:03
8	Lew Choon Hean	0.00 s	C++	2025-05-04 06:32:49
9	Winston Cat	0.00 s	C++	2025-09-14 15:25:40
10	Tamoghno Banerjee	0.00 s	C++	2025-12-07 23:34:35

#	User	Runtime	Language	Date
1	Hidden user	0.09 s	Common Lisp	2019-07-11 09:34:00

#	User	Runtime	Language	Date
1	Harrison Shen	0.02 s	Go	2021-11-04 01:50:18
2	Erlend Fonnes	0.12 s	Go	2021-05-19 00:11:28
3	Aleksandar Mitic	0.13 s	Go	2016-12-24 18:20:01

#	User	Runtime	Language	Date
1	Brent Yorgey	0.01 s	Haskell	2025-02-07 03:25:45
2	Øyvind Almli	0.02 s	Haskell	2021-05-19 12:51:20
3	Morten Lohne	0.24 s	Haskell	2018-04-17 23:38:09
4	Birk Tjelmeland	0.25 s	Haskell	2018-05-23 20:11:12

#	User	Runtime	Language	Date
1	David Brink	0.10 s	Java	2017-01-05 21:34:25
2	Bob Joe	0.10 s	Java	2017-11-06 22:55:53
3	Matthew Zhang	0.10 s	Java	2017-11-08 18:22:20
4	Fredrik Lygre Bergesen	0.10 s	Java	2018-05-03 22:02:20
5	Anil Ghimire	0.10 s	Java	2018-05-27 03:16:53
6	Erik Baalhuis	0.11 s	Java	2015-10-04 23:09:34
7	Robert Slutsky	0.11 s	Java	2017-11-07 13:06:47
8	Joakim Kårstad Tran	0.11 s	Java	2018-05-08 19:26:39
9	Eyleifur Bjarkason	0.11 s	Java	2018-12-18 22:47:03
10	Sawyer Stanley	0.11 s	Java	2022-08-05 01:02:52

#	User	Runtime	Language	Date
1	Christian Pilegaard Cederquist	0.03 s	JavaScript (SpiderMonkey)	2023-08-13 14:08:52
2	Bjørn Chr. Soltvedt	0.31 s	JavaScript (SpiderMonkey)	2016-10-30 18:31:14

#	User	Runtime	Language	Date
1	Hidden user	0.38 s	Julia	2025-04-22 09:13:23
2	Timothy Gaede	0.94 s	Julia	2024-09-03 09:05:15

#	User	Runtime	Language	Date
1	Phường Lên	0.29 s	Kotlin	2020-02-03 21:38:01
2	Simon Lindhen	0.30 s	Kotlin	2018-10-07 15:51:30
3	Hidden user	0.30 s	Kotlin	2020-02-26 23:42:12
4	Adam Koprowski	0.32 s	Kotlin	2021-04-06 19:24:49
5	poppyer	0.32 s	Kotlin	2022-07-18 18:10:31

#	User	Runtime	Language	Date
1	Oskar Haarklou Veileborg	0.05 s	Python 2	2015-04-25 13:45:58
2	Asger Hautop Drewsen	0.05 s	Python 2	2015-11-01 15:55:33
3	Agis Daniels	0.05 s	Python 2	2020-06-08 15:41:07
4	Patrik Lilja	0.06 s	Python 2	2015-10-22 23:27:18
5	Johan Lyts	0.06 s	Python 2	2020-01-22 15:19:51
6	Lars Tveito	0.08 s	Python 2	2015-10-27 00:55:32
7	Greg Hamerly	0.08 s	Python 2	2015-12-15 23:32:24
8	Tomas Alvarez	0.08 s	Python 2	2017-09-11 20:44:11
9	Daniel Widmer	0.08 s	Python 2	2018-04-18 18:28:00
10	Øyvind Haarberg	0.09 s	Python 2	2018-04-20 16:01:06

#	User	Runtime	Language	Date
1	Bjørn Dons	0.05 s	Python 3	2019-02-22 03:37:17
2	Sander Oppen	0.05 s	Python 3	2024-10-28 21:23:59
3	Nhự Nương Họ Vũ	0.05 s	Python 3	2025-03-25 21:30:17
4	Xiaoyang Xu	0.05 s	Python 3	2025-11-28 02:32:46
5	Ruizhe Jiang	0.05 s	Python 3	2025-12-06 06:10:07
6	Ocram Esah	0.06 s	Python 3	2022-02-15 20:37:45
7	Agis Daniels	0.07 s	Python 3	2020-06-08 15:40:37
8	Sidharth Sundar	0.07 s	Python 3	2021-04-12 00:33:57
9	András Biczó	0.07 s	Python 3	2023-04-16 23:59:05
10	Ole Vik Lysne	0.07 s	Python 3	2025-05-24 14:39:00

#	User	Runtime	Language	Date
1	Thomas Feld	0.06 s	Ruby	2023-08-14 09:59:06
2	Donald Dong	0.23 s	Ruby	2019-04-18 05:51:21
3	Zohar Malamant	0.62 s	Ruby	2018-04-21 01:25:16

#	User	Runtime	Language	Date
1	Vincent Lagerros	0.00 s	Rust	2024-02-02 17:57:03
2	Yoeri Otten	0.07 s	Rust	2022-11-16 15:43:15
3	Jonathan Choi	0.07 s	Rust	2024-04-15 05:59:29
4	Artur Khuziakhmetov	0.07 s	Rust	2025-01-28 09:22:31
5	Arnav Sastry	0.09 s	Rust	2021-08-16 23:45:45

#	User	Length	Language	Date
1	Ivan Petrov	2239	C	2019-11-11 09:21:56
2	Ali A. Alrufaiee	2395	C	2022-09-02 03:49:27
3	Aman Banti	2395	C	2023-06-01 16:14:31
4	Fahmi Dinsefa	2396	C	2023-07-09 14:37:52
5	Minhajur Rahman	2397	C	2021-07-17 17:46:50
6	hk	2398	C	2022-10-22 12:46:21
7	Daniel Worsnup	2478	C	2016-05-01 06:47:18
8	David Hinschberger	2486	C	2018-04-11 00:25:59
9	Tandin Wangchuk	2486	C	2019-06-02 16:10:10
10	i_love_ pickles	2486	C	2019-11-26 16:06:11

#	User	Length	Language	Date
1	Gustav Kalander	2836	C#	2018-06-11 19:43:06
2	Mike Garrett	2905	C#	2019-03-04 05:16:21
3	Thang Le Huu	3171	C#	2019-11-28 06:09:37
4	Sjoerd Teunisse	4018	C#	2019-09-30 21:03:22
5	Kelvin Snepvangers	4308	C#	2018-10-06 22:47:32

#	User	Length	Language	Date
1	Johan Wind	834	C++	2016-04-15 18:24:05
2	David Zheng	916	C++	2018-12-22 23:33:22
3	Malcolm Karutz	941	C++	2019-03-04 09:29:53
4	Geir-Arne Fuglstad	982	C++	2015-04-25 12:46:11
5	Christian Yongwhan Lim	1006	C++	2023-06-23 18:17:48
6	Kaze Ashitano	1023	C++	2020-10-20 12:45:47
7	Mukerem Ali Nur	1045	C++	2019-11-19 10:02:20
8	Brage Isak Keiserås Bakkane	1062	C++	2021-05-24 17:36:52
9	Markus Mathiasen	1064	C++	2023-08-17 22:27:41
10	Kyle Perry	1084	C++	2024-04-11 08:28:03

#	User	Length	Language	Date
1	Hidden user	1092	Common Lisp	2019-07-11 09:34:00

#	User	Length	Language	Date
1	Erlend Fonnes	1144	Go	2021-05-19 00:11:28
2	Harrison Shen	1438	Go	2021-11-04 00:29:29
3	Aleksandar Mitic	2952	Go	2016-12-24 18:20:01

#	User	Length	Language	Date
1	Birk Tjelmeland	640	Haskell	2018-05-23 20:11:12
2	Morten Lohne	1206	Haskell	2018-04-23 17:16:42
3	Øyvind Almli	1447	Haskell	2021-05-19 00:50:06
4	Brent Yorgey	2814	Haskell	2021-03-20 11:59:05

#	User	Length	Language	Date
1	Caeden Whitaker	712	Java	2021-12-22 19:27:00
2	Michael Zündorf	754	Java	2019-02-12 23:31:14
3	Taylor Wong	854	Java	2024-04-14 04:52:32
4	Ng Tze Henn	877	Java	2023-07-29 16:32:35
5	Martin Wan	898	Java	2017-11-05 08:58:56
6	Dick Ong	901	Java	2023-08-03 08:46:50
7	Tan Wei Seng	909	Java	2023-04-12 05:21:36
8	Jan Štola	924	Java	2015-06-07 20:52:24
9	Jeremy Archer	927	Java	2015-05-02 19:18:29
10	Sam Reinehr	982	Java	2018-09-13 00:37:36

#	User	Length	Language	Date
1	Bjørn Chr. Soltvedt	995	JavaScript (SpiderMonkey)	2016-10-30 18:31:14
2	Christian Pilegaard Cederquist	2365	JavaScript (SpiderMonkey)	2023-08-13 14:08:52

#	User	Length	Language	Date
1	Hidden user	655	Julia	2025-04-22 09:13:23
2	Timothy Gaede	5653	Julia	2024-09-03 09:05:15

#	User	Length	Language	Date
1	poppyer	959	Kotlin	2022-07-18 18:10:31
2	Adam Koprowski	974	Kotlin	2021-04-06 19:24:49
3	Hidden user	1281	Kotlin	2020-02-26 23:42:12
4	Phường Lên	1694	Kotlin	2020-02-03 21:38:01
5	Simon Lindhen	2614	Kotlin	2018-10-07 15:51:30

#	User	Length	Language	Date
1	Tore Norderud	452	Python 2	2015-04-25 18:30:19
2	Herbert Ilhan Tanujaya	510	Python 2	2019-05-03 18:02:10
3	Lars Tveito	631	Python 2	2015-10-27 00:55:32
4	Patrik Lilja	691	Python 2	2015-10-22 23:27:18
5	Guan Yang Ze	747	Python 2	2020-02-11 17:53:03
6	Alex Lewin	766	Python 2	2020-02-19 01:20:56
7	Ragur Krishnan	792	Python 2	2018-12-22 20:22:41
8	Balder Søholt Halmrast	819	Python 2	2015-04-25 12:45:52
9	RandyWaterhouse	831	Python 2	2021-08-14 08:27:27
10	Haggai Liu	833	Python 2	2017-06-15 07:19:25

#	User	Length	Language	Date
1	Benjamin Z White	192	Python 3	2023-06-08 21:28:16
2	Peter Stauder	313	Python 3	2023-01-13 22:04:12
3	Jason Clarke	402	Python 3	2024-04-09 15:39:40
4	Ahmed Chamseddine	406	Python 3	2026-02-13 11:10:02
5	Hrant Hovhannisyan	407	Python 3	2026-01-23 05:08:43
6	Teikn Smith	425	Python 3	2024-08-02 06:14:11
7	Xiaoyang Xu	506	Python 3	2025-11-28 01:58:42
8	Bryan Wong Wei Heng	534	Python 3	2020-04-08 15:11:06
9	Timothy White	551	Python 3	2023-03-11 05:09:12
10	Jerry Xu	585	Python 3	2026-02-18 21:41:07

#	User	Length	Language	Date
1	Thomas Feld	108	Ruby	2023-08-14 10:26:48
2	Zohar Malamant	340	Ruby	2018-04-21 01:25:16
3	Donald Dong	544	Ruby	2019-04-18 05:51:21

#	User	Length	Language	Date
1	Artur Khuziakhmetov	1219	Rust	2025-01-28 09:22:31
2	Yoeri Otten	2549	Rust	2022-11-16 15:43:15
3	Vincent Lagerros	2694	Rust	2024-02-02 17:57:03
4	Arnav Sastry	2942	Rust	2021-08-16 23:45:45
5	Jonathan Choi	4509	Rust	2024-04-15 05:59:29

Solution running time distribution