Problem A
Head Guard — Problem Statistics

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Submissions	1626
Accepted submissions	682
Submission ratio	41.94%
Authors	654
Full solves [?]	583
Full solve Ratio	89.14%

#	User	Runtime	Language	Date
1	Chenzhang Hu	0.06 s	Bash	2023-12-19 15:07:05

#	User	Runtime	Language	Date
1	Mikael Fiala-Lundström	0.02 s	C#	2022-03-12 23:15:06
2	Henrik Hallbert	0.02 s	C#	2022-03-17 09:22:28
3	Göran Andersson	0.02 s	C#	2022-05-19 12:39:40
4	Yuwono Bangun Nagoro	0.02 s	C#	2022-08-16 19:13:40
5	Eric Weiss	0.02 s	C#	2022-09-09 20:50:21
6	Linnea Bergman	0.02 s	C#	2022-09-15 13:54:06
7	Cameron Cunningham	0.02 s	C#	2023-04-03 22:44:41
8	Masroor Aijaz	0.03 s	C#	2024-04-24 10:41:35
9	Junior Quintana	0.04 s	C#	2023-06-24 20:35:52
10	Umar Rasyid	0.04 s	C#	2025-07-09 21:22:27

#	User	Runtime	Language	Date
1	Jacob Harris Cryer Kragh	0.02 s	F#	2022-10-30 15:10:33

#	User	Runtime	Language	Date
1	Norbert Voelker	0.08 s	Go	2022-03-22 00:18:55

#	User	Runtime	Language	Date
1	Ng Tek In	0.00 s	Haskell	2022-08-16 18:57:24
2	Hidden user	0.00 s	Haskell	2023-01-03 11:44:19
3	Hidden user	0.01 s	Haskell	2022-03-05 20:06:59
4	Aaron Lengyel	0.01 s	Haskell	2022-03-10 09:21:00
5	Brent Yorgey	0.01 s	Haskell	2022-03-14 04:09:09
6	Zach Tschetter	0.01 s	Haskell	2022-03-30 07:32:35
7	Steinar Simonnes	0.01 s	Haskell	2024-03-23 15:05:17

#	User	Runtime	Language	Date
1	LEE DE EN	0.04 s	Java	2024-08-27 15:28:49
2	Bjørn Dons	0.06 s	Java	2022-03-26 21:27:30
3	Crystal Sharpe	0.06 s	Java	2022-03-29 03:53:24
4	Sven Rönnbäck	0.06 s	Java	2022-05-12 21:12:29
5	Logan Pipes	0.06 s	Java	2022-05-31 00:19:16
6	Sawyer Stanley	0.06 s	Java	2022-05-31 00:29:42
7	Mack Wong Yoong Yee	0.06 s	Java	2024-02-19 16:57:57
8	Mark Sturtevant	0.06 s	Java	2024-10-10 03:46:08
9	Stela Palii	0.07 s	Java	2022-03-14 17:09:47
10	Eric Neo	0.08 s	Java	2022-10-19 21:38:41

#	User	Runtime	Language	Date
1	Ahmed Mustafa Malik	0.05 s	JavaScript (Node.js)	2024-04-24 11:05:54
2	Muhammad Fahad	0.05 s	JavaScript (Node.js)	2024-04-24 11:27:21
3	Juthi Sarker Aka	0.05 s	JavaScript (Node.js)	2024-04-27 16:17:00
4	Juthi Sarker Aka	0.05 s	JavaScript (Node.js)	2024-04-27 16:52:01
5	Samuel Högfeldt	0.08 s	JavaScript (Node.js)	2022-08-27 12:47:21
6	Spiros Kalamaris	0.09 s	JavaScript (Node.js)	2023-02-01 18:13:00
7	George Kamtziridis	0.09 s	JavaScript (Node.js)	2023-02-03 10:56:11
8	Ster Sar	0.09 s	JavaScript (Node.js)	2023-02-03 11:37:15
9	Christina Konstantinidou	0.09 s	JavaScript (Node.js)	2023-02-03 12:10:54

#	User	Runtime	Language	Date
1	Bjørn Chr. Soltvedt	0.02 s	JavaScript (SpiderMonkey)	2022-03-10 19:09:23
2	Christian Pilegaard Cederquist	0.02 s	JavaScript (SpiderMonkey)	2023-01-27 23:06:25
3	Jimmy Gustafsson	0.02 s	JavaScript (SpiderMonkey)	2025-07-24 21:10:04

#	User	Runtime	Language	Date
1	Timothy Gaede	0.54 s	Julia	2024-04-11 02:04:45
2	Danny Robinson	0.56 s	Julia	2023-10-31 15:03:38

#	User	Runtime	Language	Date
1	Zaw Myat	0.19 s	Kotlin	2024-01-14 07:31:42
2	Adam Rankin	0.20 s	Kotlin	2023-04-25 21:23:59
3	Aniket Kumar	0.20 s	Kotlin	2024-04-23 19:17:08

#	User	Runtime	Language	Date
1	Ingemar Ragnemalm	0.00 s	Pascal	2023-06-08 21:28:31

#	User	Runtime	Language	Date
1	Renate	0.01 s	PHP	2022-07-25 23:47:27

#	User	Runtime	Language	Date
1	Andriy Zyevakov	0.02 s	Prolog	2023-02-08 18:36:05
2	Hakan Kjellerstrand	0.02 s	Prolog	2023-03-06 19:30:39

#	User	Runtime	Language	Date
1	Yanmarshus Bachtiar	0.03 s	Python 2	2022-03-12 04:26:54
2	Andreas Björklund	0.03 s	Python 2	2022-03-13 18:56:34
3	Johan Lyts	0.03 s	Python 2	2022-03-31 21:49:19
4	Ocram Esah	0.03 s	Python 2	2022-04-14 11:34:02

#	User	Runtime	Language	Date
1	Suus Brommer	0.04 s	Python 3	2022-06-05 09:46:05
2	Weiguo Jiang	0.04 s	Python 3	2022-06-13 03:28:26
3	Peter Stauder	0.04 s	Python 3	2022-06-17 11:08:19
4	Petr	0.04 s	Python 3	2022-07-02 20:16:07
5	Kenneth Jensen	0.04 s	Python 3	2022-07-06 12:13:16
6	Rajul Srivastava	0.04 s	Python 3	2022-07-16 11:58:37
7	Mukerem Ali Nur	0.04 s	Python 3	2022-07-19 13:58:15
8	Kefiyalew Kunta	0.04 s	Python 3	2022-07-19 14:59:06
9	Yeabsra Ayehualem	0.04 s	Python 3	2022-07-19 17:26:03
10	Kattis Speedrun	0.04 s	Python 3	2022-07-22 00:55:55

#	User	Runtime	Language	Date
1	Alexander Bilde Pedersen	0.06 s	Ruby	2023-06-03 23:50:47
2	Thomas Feld	0.07 s	Ruby	2023-02-09 08:53:37
3	Chenzhang Hu	0.07 s	Ruby	2024-11-28 14:01:27

#	User	Runtime	Language	Date
1	Bas Dirks	0.00 s	Rust	2022-03-26 14:40:18
2	David Rasch	0.00 s	Rust	2022-04-23 10:18:30
3	Magix	0.00 s	Rust	2022-06-25 03:04:36
4	Emil Skydsgaard	0.00 s	Rust	2022-07-14 19:49:18

#	User	Length	Language	Date
1	Chenzhang Hu	50	Bash	2025-09-12 20:54:05

#	User	Length	Language	Date
1	Matthew Hartono	303	C	2022-11-07 16:11:03
2	Julian Duniec	311	C	2023-08-31 14:58:45
3	Martin Stensgård	349	C	2024-01-20 05:14:52
4	Mikael K Eriksson	402	C	2022-03-13 22:11:37
5	Leslie Yip	446	C	2022-09-09 15:46:34
6	Eyleifur Bjarkason	488	C	2023-07-12 15:08:17
7	Sami Al Chalati	494	C	2023-08-25 14:00:33
8	Naveen Kumar S	641	C	2025-04-21 15:34:52
9	Tyler Mulholland	658	C	2023-08-08 20:46:11
10	Joacim Wärn	726	C	2025-08-14 17:07:53

#	User	Length	Language	Date
1	Göran Andersson	641	C#	2022-05-19 12:39:40
2	Cameron Cunningham	791	C#	2023-04-03 22:44:41
3	Eric Weiss	799	C#	2022-09-09 20:50:31
4	Junior Quintana	853	C#	2023-06-24 20:35:52
5	Yuwono Bangun Nagoro	1005	C#	2022-08-16 19:13:40
6	Mikael Fiala-Lundström	1041	C#	2022-03-12 23:15:06
7	Masroor Aijaz	1041	C#	2024-04-24 10:41:35
8	Henrik Hallbert	1056	C#	2022-03-17 09:22:28
9	Umar Rasyid	1297	C#	2025-07-09 21:22:27
10	Aman Choudhary	1610	C#	2024-04-25 01:10:10

#	User	Length	Language	Date
1	鄭宇哲	247	C++	2023-12-24 09:57:47
2	Cheru Turga	252	C++	2022-07-19 16:43:20
3	Abdi Tefera	260	C++	2022-07-23 21:16:00
4	AmineF0	270	C++	2023-02-25 22:39:15
5	Nguyen Tran Huu Duc	281	C++	2022-03-14 12:44:14
6	人外沙耶	294	C++	2023-01-17 14:22:15
7	林育霆	301	C++	2024-02-10 04:38:45
8	Maverick Hartono	305	C++	2022-11-07 15:58:47
9	Grae Yeandle	315	C++	2022-03-13 11:56:46
10	Dmitry Lyubshin	319	C++	2023-04-04 13:15:32

#	User	Length	Language	Date
1	Jacob Harris Cryer Kragh	591	F#	2022-10-30 15:10:33

#	User	Length	Language	Date
1	Norbert Voelker	585	Go	2022-03-22 00:18:55

#	User	Length	Language	Date
1	Zach Tschetter	154	Haskell	2022-03-30 07:32:35
2	Hidden user	186	Haskell	2022-03-05 20:06:59
3	Steinar Simonnes	241	Haskell	2024-03-23 15:06:27
4	Brent Yorgey	312	Haskell	2022-03-14 04:09:09
5	Ng Tek In	459	Haskell	2022-08-16 18:57:24
6	Hidden user	565	Haskell	2023-01-03 11:44:19
7	Aaron Lengyel	728	Haskell	2022-03-10 09:21:00

#	User	Length	Language	Date
1	John Hershey	282	Java	2023-09-26 18:30:15
2	Evan Magill	303	Java	2023-09-25 17:50:28
3	Crystal Sharpe	488	Java	2022-03-29 03:53:24
4	Kevin Lee	555	Java	2022-03-05 20:52:24
5	Saksham Puri	587	Java	2022-03-05 20:48:34
6	Raymond Arrington	606	Java	2024-07-02 01:17:56
7	Tan Zi Yang	640	Java	2023-08-28 16:00:46
8	Marshall D Feng	645	Java	2022-03-27 20:05:42
9	Suhas T. Nagar	645	Java	2022-10-08 21:39:20
10	Ryan Hayden	650	Java	2024-01-13 23:49:10

#	User	Length	Language	Date
1	Muhammad Fahad	482	JavaScript (Node.js)	2024-04-24 11:27:21
2	Ahmed Mustafa Malik	548	JavaScript (Node.js)	2024-04-24 11:05:54
3	Samuel Högfeldt	654	JavaScript (Node.js)	2022-08-27 12:47:21
4	Juthi Sarker Aka	671	JavaScript (Node.js)	2024-04-27 16:17:00
5	Juthi Sarker Aka	671	JavaScript (Node.js)	2024-04-27 16:52:01
6	Spiros Kalamaris	835	JavaScript (Node.js)	2023-02-01 18:13:00
7	George Kamtziridis	894	JavaScript (Node.js)	2023-02-03 10:56:11
8	Christina Konstantinidou	994	JavaScript (Node.js)	2023-02-03 12:10:54
9	Ster Sar	1114	JavaScript (Node.js)	2023-02-03 11:37:15

#	User	Length	Language	Date
1	Jimmy Gustafsson	117	JavaScript (SpiderMonkey)	2025-07-24 21:10:04
2	Christian Pilegaard Cederquist	376	JavaScript (SpiderMonkey)	2023-01-27 23:06:25
3	Bjørn Chr. Soltvedt	463	JavaScript (SpiderMonkey)	2022-03-11 11:31:33

#	User	Length	Language	Date
1	Danny Robinson	64	Julia	2023-10-31 15:03:38
2	Timothy Gaede	615	Julia	2024-04-11 02:04:45

#	User	Length	Language	Date
1	Zaw Myat	524	Kotlin	2024-01-14 07:31:42
2	Aniket Kumar	537	Kotlin	2024-04-23 19:17:08
3	Adam Rankin	752	Kotlin	2023-04-25 21:23:59

#	User	Length	Language	Date
1	Ingemar Ragnemalm	334	Pascal	2023-06-08 21:28:31

#	User	Length	Language	Date
1	Renate	488	PHP	2022-07-25 23:47:27

#	User	Length	Language	Date
1	Hakan Kjellerstrand	133	Prolog	2023-03-06 19:32:25
2	Andriy Zyevakov	369	Prolog	2023-02-08 18:36:05

#	User	Length	Language	Date
1	Ocram Esah	270	Python 2	2022-04-14 11:34:02
2	Yanmarshus Bachtiar	289	Python 2	2022-03-12 04:26:54
3	Johan Lyts	361	Python 2	2022-03-31 21:49:19
4	Andreas Björklund	376	Python 2	2022-03-13 18:56:34

#	User	Length	Language	Date
1	Clement Oh	99	Python 3	2023-05-18 14:19:55
2	Benjamin Z White	109	Python 3	2023-05-06 14:01:02
3	Nguyen Duc Khang	115	Python 3	2025-09-21 08:28:44
4	Christofer Ohlsson	126	Python 3	2022-09-26 09:01:49
5	Suus Brommer	142	Python 3	2022-06-05 09:46:05
6	Thomas Feld	146	Python 3	2022-08-26 10:07:13
7	Karen Birgitta Hanssen	148	Python 3	2023-04-27 20:10:34
8	Hidden user	155	Python 3	2022-03-29 08:29:50
9	Jón Steinn Elíasson	165	Python 3	2022-10-09 22:55:16
10	Simon Baeckelant	173	Python 3	2024-04-27 10:16:16

#	User	Length	Language	Date
1	Thomas Feld	44	Ruby	2023-02-09 08:53:37
2	Chenzhang Hu	47	Ruby	2024-11-28 14:01:27
3	Alexander Bilde Pedersen	215	Ruby	2023-06-03 23:50:47

#	User	Length	Language	Date
1	Bas Dirks	569	Rust	2022-03-26 14:40:18
2	Emil Skydsgaard	677	Rust	2022-07-14 19:49:18
3	David Rasch	703	Rust	2022-04-23 10:18:30
4	Magix	1012	Rust	2022-06-25 03:04:36

Solution running time distribution