CEOI 2026

Sunday, 05. July 2026 (Albert)

We met at around 9 in Zürich. And then our long and special train journey with 5 changes began. Of course, in Switzerland there was no problem at all with the change in Buchs where we ‘only’ had 3 minutes. In Liechtenstein we had to take two different busses to cross it and somehow decided that the main station is basically just a playground. To my surprise, all of the trains were punctual. Some over 10 hours later we arrived in Villach where we only had 6 minutes to get from platform 2 <= platform <= 6 to platform 8 which was far away. We managed to get on the train, only to realize that it was a different train and that ours left from a different platform. Since the next train left in 2 hours, we decided to eat breakfast in a restaurant in Villach.

2 hours later we got on the train going to Ljubljana. When we arrived, our guide was already waiting for us on the platform. We only had to walk 20 minutes to the bus, because of course we missed the last bus that was more direct. After walking there, we figured out that of course, we wanted to get on the last bus which obviously decided not to exist. Therefore, we had to walk another 15 minutes. Within the bus, we learned about the payment system that CEOI figured out for public transport. Each guide received a card to pay. But the card always declined since there was no money on it. But the system tracked, how often each card was declined and then sent a bill to CEOI. This meant that on every bus, we had to decline our card 7 times which was kind of awkward. Plenty of time later, we arrived at the dormitory, where the receptionist gave us an introduction. But first, how we will go about it, first giving our ID’s, then something… then choosing our rooms, then something… She for some reason always told us the whole procedure and always just inserted a string when we asked her about something. Imagine this but longer:

Her:

We will first check ID’s then the girls will choose their rooms, then the leaders, then the boys and then I will show you around.

Aliaksei:

Could I put something in a fridge because it has to be cooled?

Her:

Ok, we will first check out the fridge, then we will check ID’s then the girls will choose their rooms, then the leaders, then the boys and then I will show you around.

Aliaksei:

At what temperature is the fridge?

Her:

Ok, so first we will check the temperature of the fridge, then we will put your stuff in the fridge, then we will check ID’s then the girls will choose their rooms, then the leaders, then the boys and then I will show you around.

This continued for a long time until we realized that asking questions is a stupid idea. Around midnight we managed to get to our rooms.

Monday, 06. July 2026 (Albert)

Yes, today’s date actually is 67 but it wasn’t mentioned as far as we know. It was a normal day with the practice session followed by lunch and the opening ceremony. Turns out, we had to walk to the contest site every day, usually on the bicycle lane. At the practice session I once again realized how good the Swiss contest environment is. At CEOI we had some very minimal window manager which didn’t even support the super (Windows) key and generally was super annoying. Also, the debugger in VS Code didn’t work for me, some people figured out that some AI wasn’t disabled… Basically, it was broken and they had one day to fix it.

Lunch was fine, nothing special, but then we had another adventure with the buses. We had to get on a bus to get to the school where the opening ceremony was. That bus was full so we were told to wait 40 minutes for the next one, which should still arrive early enough. Well, if and only if it even appeared. Turns out, that bus didn’t exist. The guide wanted us to wait another 40 minutes for the next bus, but we decided to leave her and walk by ourselves to a different bus station. This decision turned out to be very good because we still arrived for the apéro and the other did not. Sadly, we didn’t have a decline card though. After the ceremony we ate ice cream and visited a castle together with the Germans. Then some of us walked home while the other’s used the German team’s decline card which they managed to get from their guide.

Tuesday, 07. July 2026 (Laetitia)

After breakfast, we walked to the University of Ljubljana, where the contest was held. As usual, the contest consisted of three tasks and lasted five hours. After the contest, we went to the canteen for lunch. The lunch break was quite long, so we had time to play Tichu and Crazy Time. After the lunch break, we had a solution presentation. Since we’d had a five-hour contest that morning, our concentration wasn’t very high. In the evening, we had a JetBrains night. First, we took part in a quiz in groups of four. The first round was quite easy. We had to recognise different logos, like the CEOI 2026 logo or the JetBrains logo. In the next round, the quiz got harder. We had to name the artist and title of various music albums, identify the actor and movie behind different memes, or recognise the music from different computer games. Unfortunately, our group wasn’t very good at this, and we ended up 15th out of 19. The top three groups won small prizes. After the quiz, we had time to play some games. We managed to convince the Austrian team to play Crazy Time with us. After a while, we had to clear the table, since pizza had arrived for dinner. The pizzas were enormous, each one covering an entire table. After dinner, we walked back to the accommodation, and before going to sleep, we played a few more games.

Wednesday, 08. July 2026 (Aliaksei)

On Wednesday we had the long awaited excursion day. But before that, we could choose the location of where we want to go. The options were the following:

1. Bled Castle
2. Bled Island
3. Adventure park
4. Beach volleyball

The numbers of participants per group looked somewhat like this:

As you can see in the chart, exactly 0 people chose beach volleyball, which I find quite hilarious.

The Swiss delegation was split between the island and the castle, I was in the latter group. First, we took a boat ride across the lake, debating with the German delegation if the lake’s beautiful blue color was natural. We arrived at the conclusion that we didn’t arrive at a conclusion.

The first thing we saw when we arrived to the island was a sign saying swimsuits are prohibited. This sparked the first quote of the day:

I sure hope y’all didn’t forget your clothes

• someone from the German team

The island itself was quite nice. We visited the church and rang the wishing bell (which had a 5 second delay after every input), the clocktower and the museum.

After that, Myriam introduced me to the wonderful game that is Stofl Sweep (see end of Slovak Camp blogpost). It is similar to minesweeper, but more fun and filled with SOI inside jokes. From it also stems the next quote of the day:

I think I know how toilets generate.

Wait, so how do toilets generate?

• Myriam, Alex

After taking the boat back to the beach, the group found itself with a lot of spare time, because people weren’t as late as expected. So, what does one do in that situation?

The correct answer turns out to be, go straight on to the bus, go straight on in the opposite direction, and go straight on to the bus for the last time. And then still arrive early for lunch at the restaurant.

After lunch we went to Radovljica - the second excursion location. There we visited a gingerbread workshop, where we could decorate our own (sadly inedible) gingerbread hearts, and a beekeeping museum. During the latter visit, we were rather tired and sleep deprived. But as always at SOI, if there’s an interactive screen, we have to display something unintended on it. For example, xkcd:

On the bus ride back we were all very tired and sleepy and so not much happened there.

Despite the next day being a contest day, some people still decided to sleep deprive themself. I however was a responsible participant, and went to sleep at a reasonable time.

Thursday, 09. July 2026 (Myriam)

Thursday was the second contest day, so after a ridiculously low amount of people at breakfast (also since there was obviously no quarantine, some of them were leaders), we were ready to go to the university at 7:30*, as written in the schedule. But a lot of guides had told their teams they would leave at 8 and our guide never actually arrived, so we went to the contest hall with other teams. For the contest, the first task strangely had only one sample, but it actually had a decent size! Also, we got our first and only useful subtask of the contest, where we had to consider a complete graph. Also, the testcases were so weak, multiple people got the general subtask without fullscoring (there were actually no complete graphs in multiple subtasks). But at least it was clear that it was weak testcases and not something else. The second task a dp that had multiple sample! I know, it’s crazy! The third task was just really painful, let’s not talk a lot about it. After the contest, we had lunch and then testing (where we definitely went), solution presentation (where we were definitely on time) and a presentation about AI (during which I was definitely not playing Twin It and Set outside of the room). We also got the usual QuantCo mocktail, and then the closing ceremony. During the closing ceremony, Daphne showed once again how Swiss she is by standing behind the Swiss flag, and the rest of the Germans also used the blau Drache as the official German flag. Also, every medalist got a Jetbrain goodie bag. Guess what goodies were inside? Apart of the Jetbrain plushy, we got … (drumroll) … A pair of socks! So nice! Also, when I went on the stage to get my medal, the rest of the team threw the chocolates (if you’re wondering why at the closing and not the opening, go read Monday’s blogpost). And at some point, we realized there was an SOI card deck that was randomly put on the desk on the stage. And then the guy who was doing the ceremony saw it, asked everyone if we knew what it was, I said it was a Swiss card deck, he completely ignored me, and then he said there was a zero on the first card (it was the red as, he thought the EGOI logo was a big zero!) so it was linked to informatics because of binary numbers! At the end of the ceremony, I went to take it, and it had disappeared! One of the Hungarian participants had taken it since he thought no one claimed it to be his. But because none of us knew how the deck got there, we decided to give it to the Hungarian. Well, now that you have a first idea of the guy presenting the ceremony, let’s tell you a bit more! (Only, a bit, it would be too long otherwise.) At some point, the photograph asked him to change slides for one of the pictures with the gold medalists, and the presenter struggled so much the photograph did it himself! Also, after learning CEOI 2027 will be in Poland, we watched a video about it, and at some point, the Polish representant asked the presenter to pause the video, and he took so much time searching for his glasses that the moment was passed, so the Polish told him it was fine. A few minutes later, after everyone had already forgotten about that, the presenter actually did press pause! Whatever. After the ceremony, we had the banquet at the university, which sounds bad, but it was actually pretty good, like a fancy buffet and not university food. After dinner, we went back to the dormitory where we played games for a few* hours with other delegations.

Friday, 10. July 2026 (Laetitia)

On Friday, we ate breakfast quite early because we had a long trip ahead of us with 6 different trains. Our first train went from Ljubljana main station to Villach in Austria. Since we were all still tired, we listened to some music or tried to sleep. Only 20 km from Villach, the train suddenly stopped in the middle of nowhere, and we didn’t get any information. Luckily, the train continued 30 minutes later, though we ended up missing our connecting train. It didn’t matter much, as there were enough trains in our direction and all the later trains arrived on time. During the rest of the ride, we played different games: Tichu, something between Mao and Crazy Time and a very stupid card game (as our concentration was quite bad by the end of the trip). We arrived at Zurich main station shortly after nine, hoping to buy food at Rice Up, but unfortunately, it had closed a few minutes earlier. After we all bought dinner at a different place, we individually went home.