The fifth hint will be published on 2nd January, 13:00 GMT.
By 26th December, 13:00 GMT, there are 1016 participants from 78 countries. 166 solutions to P1 were submitted, out of which 65 were correct.
Correct solutions by university students:
| First name | Surname | Country | School/University | Date time |
| Yuechen | Zhu | China | Peking University | 21/11/2021 13:53:00 |
| Alessandro | Rezzi | Italy | University of Padova | 21/11/2021 17:59:00 |
| Zhening Li | Eddie Chen | Canada/United States | Massachusetts Institute of Technology | 22/11/2021 06:17:00 |
| Tasuku | Ono | Japan | Harvard University | 22/11/2021 17:17:00 |
| Tarun | Agarwal | India | Hasn’t started yet | 22/11/2021 18:16:00 |
| Ameya | Deshmukh | India | IIT Bombay | 23/11/2021 07:47:00 |
| Yeswanth Narayana | Patnana | India | Indian institute of technology Madras | 23/11/2021 08:59:00 |
| Isaac | Wu | Australia | University of Melbourne | 25/11/2021 05:03:00 |
| Kyle | Bomeisl | United States | Rutgers University | 27/11/2021 03:49:00 |
| Cheng Wei | Lin | Taiwan | National Cheng Kung University | 29/11/2021 09:05:00 |
| Jaroslav | Herman | Czech Republic | Charles University | 01/12/2021 21:12:00 |
| Victor | Lequin | France | École Normale Supérieure PSL | 04/12/2021 20:10:00 |
| Arhaan | Ahmad | India | Indian Institute of Technology, Bombay | 04/12/2021 21:30:00 |
| Ricards | Knipsis | Latvia | University of Manchester | 05/12/2021 00:46:00 |
| Vinícius | Ferreira Rodrigues | Brazil | Universidade de São Paulo | 05/12/2021 03:54:00 |
| Erik | Sünderhauf | Germany | Technical University of Munich | 05/12/2021 15:18:00 |
| Tejas | Acharya | India | University of Oxford | 06/12/2021 17:03:00 |
| Yanjun | Zhou | China | University of Oxford | 07/12/2021 01:03:00 |
| Pom-pom | Tovey | Singapore | University of Oxford | 07/12/2021 21:04:00 |
| Deng | Jinqiu | China | Beijing University of Aeronautics and Astronautics | 08/12/2021 14:36:00 |
| Kevin | You | United States | Carnegie Mellon University | 12/12/2021 01:48:00 |
| Ameya Vikrama | Singh | India | Indian Institute of Technology Bombay | 12/12/2021 11:51:00 |
| Qian | Lin | China | University of Oxford | 14/12/2021 15:31:00 |
| Ilari | Mäkinen | Finland | Aalto University | 14/12/2021 18:02:00 |
| Daoxin | Zhong | Singapore | University of Oxford | 16/12/2021 21:46:00 |
| Soumyadeep | Sarma | India | Indian Institute of Science | 20/12/2021 12:52:00 |
Correct solutions by pre-university students:
| David | Constantinescu | Romania | International Computer High School of Bucharest | 21/11/2021 16:58:00 |
| Luca | Milanese | Italy | Liceo “Leonardo da Vinci”, Terracina | 21/11/2021 23:04:00 |
| Minh Hoàng | Lê | Viet Nam | HUS High School for Gifted Students | 22/11/2021 04:31:00 |
| Filip | Vučić | Croatia | I. gymnasium Zagreb | 22/11/2021 08:57:00 |
| Alexandar | Roussev | Bulgaria | First Language School | 23/11/2021 11:26:00 |
| Dženan | Midžić | Bosnia and Herzegovina | JU Gimnazija “Bihać” | 23/11/2021 21:51:00 |
| Matej | Gelev | North Macedonia | Yahja Kemal | 23/11/2021 22:18:00 |
| Sebastián | Arévalo | El Salvador | Instituto Emiliani | 24/11/2021 04:08:00 |
| Vlad-Ștefan | Oros | Romania | “Grigore Moisil” Theoretical High School | 24/11/2021 14:10:00 |
| Adam | Džavoronok | Slovakia | Gymnázium Poštová 9 | 25/11/2021 17:30:00 |
| Gabriel | Morais Barros | Brazil | Master | 26/11/2021 18:14:00 |
| Absur Khan | Siam | Bangladesh | Gap Year | 27/11/2021 16:46:00 |
| Vladimir George | Necula | Romania | International Computer High School of Bucharest | 05/12/2021 02:15:00 |
| Kanishk | Prakhar | India | City Montessori School Gomtinagar Campus-2 | 05/12/2021 09:34:00 |
| Mayank | Anand | India | FIITJEE | 05/12/2021 17:52:00 |
| Matheus | Felipe Ramos Borges | Brazil | Colégio Christus | 05/12/2021 21:30:00 |
| Felipe | Souza Lima Rocha | Brazil | (Gap) | 05/12/2021 21:30:00 |
| Alptürk | Eski | Turkey | Erbakır Science High School | 06/12/2021 05:25:00 |
| YI-TING | LIN | Taiwan | Taichung First Senior High School | 06/12/2021 14:50:00 |
| Karthik | Prakash | India | Vaels International School | 07/12/2021 10:33:00 |
| Emir | Akdağ | Turkey | Bahcesehir Highschool of Science and Technology | 11/12/2021 09:13:00 |
| Watcharakorn | Suttipong | Thailand | Triam Udom Suksa School | 11/12/2021 13:15:00 |
| Gigi | Tsirekidze | Georgia | LEPL Kutaisi Andria Razmadze physics and mathematical public school N41 | 11/12/2021 18:23:00 |
| Rhythm | Kedia | India | Lord Buddha Public school | 12/12/2021 12:26:00 |
| Vuk | Hip | Serbia | Mathematical Grammar School | 12/12/2021 12:28:00 |
| David Michael | Indraputra | Indonesia | SMAK Penabur Gading Serpong | 12/12/2021 14:37:00 |
| Sam | Sooter | United States | Homeschooled | 12/12/2021 16:15:00 |
| Marius | Frija | Moldova | LT „Orizont” | 12/12/2021 20:29:00 |
| Kaan | Dere | Turkey | Bahcesehir High School for Science and Technology | 12/12/2021 21:04:00 |
| Ahmet Bahadır | TRABZON | Turkey | Kabatas Erkek High School | 14/12/2021 18:38:00 |
| Divyansh | Pandey | India | KV Picket | 18/12/2021 17:30:00 |
| Gurbhit | Chaurakoti | India | KV INDIAN MILITARY ACADEMY DEHRADUN | 18/12/2021 17:39:00 |
| Chengkai | Yu | China | The High School Affiliated to Renmin University of China | 19/12/2021 12:51:00 |
| Akshat | Shrivastava | India | Krishna public school, nehru nagar | 19/12/2021 20:15:00 |
| Yehyun | Choi | United States | Westlake High School | 20/12/2021 09:42:00 |
| Miguel Isaías | Doradea Meléndez | El Salvador | Insituto Emiliani | 20/12/2021 19:27:00 |
| Balázs Csaba | Kovács | Hungary | Hatvani Bajza József Gimnázium | 24/12/2021 16:28:00 |
| Hoang Duong | Vu Ngo | Viet Nam | HUS High school for Gifted Student | 25/12/2021 19:56:00 |
| Emerson Franzua | Aldana Gavarrete | Honduras | School | 26/12/2021 04:39:00 |
The list of countries:
Algeria, Argentina, Australia, Azerbaijan, Bangladesh, Belarus, Belgique, Bosnia and Herzegovina, Brazil, Brunei Darussalam, Bulgaria, Canada, China, Costa Rica, Croatia, Czech Republic, Egypt, El Salvador, Estonia, Ethiopia, Finland, France, Georgia, Germany, Greece, Honduras, Hong Kong, Hungary, India, Indonesia, Iran, Israel, Italy, Japan, Kazakhstan, Korea, Kosovo, Kyrgyzstan, Latvia, Lebanon, Lithuania, Luxembourg, Macao, Malaysia, Mexico, Moldova, Mongolia, Nepal, Nigeria, North Macedonia, Pakistan, Peru, Philippines, Poland, Romania, Russia, Saudi Arabia, Serbia, Singapore, Slovakia, South Africa, Spain, Sri Lanka, Suriname, Sweden, Switzerland, Syria, Taiwan, Tajikistan, Tanzania, Thailand, Turkey, Turkmenistan, Ukraine, United Kingdom, United States, Uzbekistan, Vietnam