In total, 88 solutions were submitted for problem 3, of which 29 were correct. Congratulations to everyone who successfully solved it!
There were 13 correct solutions submitted before the first hint was published, and only those were considered as candidates for the best solution awards.
The award winners are as follows.
Alon Hart (bonus: 0.4 pts) combines circuit duality with superposition of two rotated excitations. This establishes the relation between the original and dual input impedances, giving the answer with very little algebra.
Artyom Eryomin (bonus: 0.4 pts) introduces an auxiliary excitation whose phase advances by a quarter-cycle between successive terminals. This clever use of rotational symmetry reduces the infinite circuit to two scalar equations; superposing opposite phase sequences then recovers the required excitation.
Joshua Wang (bonus: 0.1 pts) replaces the infinite four-terminal tail by a square network with edge and diagonal impedances. The two unknown impedances combine into a single quantity, allowing self-similarity to determine the input impedance directly.
Shaocong Sun (bonus: 0.1 pts) expresses rotational symmetry through a cyclic-shift matrix and obtains a compact equation for the full terminal admittance matrix. Its simple symmetry modes reveal the frequency-independent response and provide a generalisation to arbitrary terminal excitations.
Final results for Problem 3
Pre-university students:
| First name | Surname | Country | School/University | P3 date time DD/MM/YY 00:00:00 | P3 Score |
| Artyom | Eryomin | Lyceum №23 | 28/12/25 17:50 | 2.4 | |
| Lee | SinHyeok | South Korea | Seoul Science High School | 29/12/25 11:28 | 1.9 |
| Kanad | Bhattacharya | India | Deeksha STEM | 4/1/26 08:23 | 1.8 |
| Antonia | Radu | Romania | Colegiul National “Mihai Viteazul” Ploiesti | 9/1/26 21:31 | 1.7 |
| Kwonheon | Lee | South Korea | Seoul Science Highschool | 11/1/26 12:17 | 1.6 |
| Siddhaarth | Dharani | Singapore | Gap Year | 15/1/26 16:48 | 1.31 |
| Qingxiang | Liao | China | Shenzhen College of International Education | 25/1/26 01:10 | 1.12 |
| Artem | Nikitin | SESC NSU | 25/1/26 11:55 | 1.1 | |
| Chetan | Malviya | India | Narayana e-Techno School, Andheri | 1/2/26 11:57 | 0.9 |
| Svarit | Joshi | India | Khyati World School | 8/2/26 08:58 | 0.7 |
| Haoze | Li | United Kingdom | Winchester College | 8/2/26 11:22 | 0.6 |
| Luka | Smiljanic | Serbia | Mathematical Grammar School | 1/3/26 11:26 | 0.5 |
| Ivan | Ermolaev | School 2044, Moscow | 5/3/26 19:34 | 0.5 |
University students:
| First name | Surname | Country | School/University | P3 date time DD/MM/YY 00:00:00 | P3 Score |
| Vaibhav | V | India | United Institute of Technology | 28/12/25 18:10 | 2.0 |
| Joshua | Wang | United States | MIT | 30/12/25 12:03 | 2.0 |
| Wang | Yixi | China | Hangzhou Dianzi University | 1/1/26 10:45 | 1.8 |
| Alon | Hart | Israel | Hebrew University of Jerusalem | 6/1/26 13:20 | 1.7 |
| Guy | Ginzberg | Israel | Open University of Israel | 2/1/26 12:11 | 1.6 |
| Ashmit | Dutta | USA | UIUC | 3/1/26 07:25 | 1.6 |
| Vinícius | Ferreira Rodrigues | Brazil | University of Iowa | 4/1/26 00:18 | 1.5 |
| Shaocong | Sun | China | Peking University | 4/1/26 04:28 | 1.5 |
| Erik | Kaniewski | Estonia | Taltech | 14/1/26 16:27 | 1.01 |
| Jonathan | Burger | Germany | Karlsruher Institut für Technologie | 16/1/26 08:49 | 0.91 |
| Igor | Kravchenko | KubSAU | 3/2/26 10:26 | 0.6 | |
| Francesco | Gariglio | Italy | Università degli Studi di Torino | 8/2/26 09:43 | 0.6 |
| Alessandro | D’Orazio | Italy | University of Pisa | 27/1/26 14:11 | 0.567 |
| Adrian | Rewkowski | Belarus | Jagiellonian University | 27/1/26 16:54 | 0.567 |
| Nikhil | Kodali | United States | UC Irvine | 1/2/26 20:42 | 0.54 |
| Larrance | United States | University of Chicago | 22/2/26 07:18 | 0.45 |