CEOI 2023 — Blog

Impressions from the Central European Olympiad in Informatics in Magdeburg, Germany, from 13-19 August 2023.

Johannes Kapfhammer

The Swiss delegation consists of Elias Bauer, Yaël Arn, Andrej Ševera and Jovian Soejono, accompanied by the team leaders Johannes Kapfhammer and Benjamin Faltin. Below we write about our experiences at this event.

Sunday, 13.08.2023 (Elias)

We met at 10 o’clock in Basel and first took the ICE to Hannover and then another train to Magdeburg. I had thought that France’s TGV was the only high-speed train in Europe but it turns out that the ICE is also just as fast. The fastest speed that I saw us going at was about 250 km/h. Thanks to the speed of the train, our journey only took about 10h in total. There was even an onboard restaurant where I was able to buy some Currywurst for lunch, a typical German dish.

When we arrived in Magdeburg, our guide for the week, Julia, was already there waiting for us. She led us to the youth hostel where we would be staying for the week. We ate dinner there together and then afterwards Julia gave us a tour of the city. As it was already quite late at that point, we decided to head back to the hostel and go to bed.

Monday, 14.08.2023 (Yaël/Andrej)

Opening Ceremony

Opening ceremony of CEOI with main organizers Wolfgang Pohl and Korinna Bade. Note the flag on the left.

This morning, 5 out of 6 people chose breakfast over sleep (Benjamin being the only sensible one). At least those weren’t late to go to the university. During the opening ceremony, we first didn’t fall asleep while German people spoke in English, which was interrupted by the CEOI balloons on the blackboard becoming the CEOI, and supported Benjamin mentally while he presented Duck Vater. As is typical for the Swiss, we were at the workshops early. We got an interesting tour of the medical research institute and then flew around in a car (absolutely in real life) (and absolutely not in the biggest mixed reality lab in Europe). After waiting for the leaders in front of the Mensa, as they had told us to do (they were inside), we ate our lunch.

The next point of the program, the practice contest, started relatively early (that is, only 10 minutes late). Yaël did a wrong submission on the binary search task but successfully solved addition. The order of the participants getting the ice creams will hopefully be the same as the final ranking (we were first). We then had to take off our extremely cool self-designed CEOI T-shirts we had been flexing with since we arrived and categorically refuse to take a team picture with a rectangular Swiss flag. During the guided city tour, we carefully listened to everything. We can remember that the tomb of Otto the Great was never opened (Benjamin was sceptical), and that we saw the oldest building and the oldest building in town (which are not the same btw).

The authors of this blog post were extremely successful at Tichu in the restaurant, which had nothing to do with having two street bombs in two consecutive rounds (and forgetting to announce the Tichu in time TWICE). We ordered a subset (to be exact a multisubset) of the menu, as we were instructed, and then got back to the youth hostel, letting Johannes go to his heaven (tasks, snacks, and a chair to sleep), also known as the translating session.

Tuesday, 15.08.2023 (Jovian)

The contest phase of the CEOI began on Tuesday. We had to wake up an hour earlier than on Monday, due to the contest starting at 9 am. The mood in the breakfast hall was subdued and soon after, we left on foot for a 20-minute hike to the university. Upon entry, we were told that our belongings would need to be kept in a locked room with only a pen being brought into the competition area. The time began soon after, and the problems were presented on the contest management system / CMS. There was an ad-hoc interactive problem, a problem based on Euler tours as well as a game problem. It seems most people found the contest challenging, as did I who scored a measly 20 points in total. (Yes, the stress was real.)

Afterwards came lunch and an analysis session, where I discovered that my Euler tour implementation was very off and fixed a bug which had prevented me from scoring 15pts. For the last activity, we were taken to the bowling alley which was found at a remote location near the highway. Two bowling rounds were played before dinner. Not long after the day was concluded with a return to the youth hostel.

Wednesday, 16.08.2023 (Yaël)

Shit [1] happens, Part 1

This morning, we were able to sleep in to recover for the contest and prepare for the one tomorrow, as it was the free day in between. Naa, actually not happening. The plan was to be outside at 7:30, and for this, we stood up at 7:00. As the average teenager will know, the plan miserably failed and only the author of this blog post was ready at that time. Luckily for the participants, the leaders were even later (with Benjamin sleeping with his alarm ringing in his hand, according to his account of the events), and everyone could get the stuff they had forgotten, including IDs, badges, and t-shirts. [3] I was the only one who didn’t go back to get something, and direly regretted it when I noticed I didn’t have my sunglasses, which made me walk around the whole day with a maximum of half an eye open. When everyone was finally down, we left for the Domplatz where our buses should have been waiting. As we walked, we noticed that we shouldn’t have worried about wearing our (not self-made flexing) CEOI-T-Shirts (Benjamin wasn’t), as this operation had been a success iff you consider 40% correct output as correct. While waiting for the buses, we also discussed about the best strategy for stealing the CEOI flag (censored by soi leaders), which is strongly secret and shouldn’t be known to the orgas. Benjamin gracefully proposed to hold the CEOI flag during the ride afterwards. We then got into the cool, small, incognito black bus as the only delegation there which made it possible for one of the most legendary Tichu rounds to take place. It happened in between the seats, with Jovian’s rucksack, which had the tendency to fall down, stuffed in between. A fail-gif worthy scene happened as Andrej let his cards fall between his seat and the door and had to retrieve them. When we arrived in Berlin, all of a sudden, our leaders had vanished. They had abandoned us! Heavily heartbroken, we proceeded to the computer game museum. There, after the first round of Find Elias™, we got a tour, getting told about the history of games which was actually interesting enough for nobody to fall asleep. As everything was quite stuffed, we only got to play some games we didn’t actually understand (they sadly didn’t have Find Elias™ in their exhibition). The very important next step was to eat. We got vegetarian sandwiches and there were quite divergent opinions about how good they were. At least the wasps really liked them, as they kept harassing us. Then we got some more sandwiches and some sandwiches, but still there where some, which were later given to some charity (great action btw). After finishing them, we where as social as always (sitting on some bench reading) and refused to become celebrities of the CEOI-YouTube channel (no product placement). We still got ourselves into the background by sheer skill. We also witnessed the German team almost being mowed over, but unluckily there are still as many competitors as before.

More shit happens, Part 2

Berlin Brandenburger Tor

The Swiss delegation with replacement team leaders in front of the Brandenburg Gate. [Note by the editor: we did not abandon them, we were just temporarily missing for half a day. In fact we got a certificate after the event certifying we have “successfully participated as Leader” which certifies that this was perfectly fine (certified).]

When we hadn’t finished the sandwiches, we waited for our guide, who didn’t find where we were at first (perfect first impression). In the end, the orgas successfully found him, and we could get back to the busses, again matching cool teams with cool bus. So, we got our private tour, and departed after saving Andrej’s arm from the door which had been very mean and imprisoned it between itself and his chair. We were welcomed with a kind “Welkom tu ze progresiw Siti tur of Berlin (Hier rechts abbiegen)”. While our bus driver was struggling to keep up with the last-second directions from the guide, we got a interesting letter about philosophy, politics, capitalism, money, pop culture, the pick-up corner and the dangerous places in Berlin, the history of west and east berlin and the importance of the current moment. During this highly educational tour, we often had big problems not to laugh. After driving around on the third lane at 10 km/h for some time, we finally stopped on the street in front of the Brandenburger Tor. There we did a photo with our replacement leaders, who, unlike the last one we had, didn’t abandon us. I very graciously, following Benjamin’s example, held the flag for them. On the second part of the trip, only a negligible amount (¼) of the participants actually managed to fall asleep.

The next event on the program was the visit of the Bundestag. There, we were surprised to find people we had thought lost for ever: our leaders! They had been on a highly secret mission maybe involving the tasks and games [4], but were not allowed to tell us what the mission really was about. They were not sure if they would be on the visitors list, as they had forgotten (you may see a recurring pattern here) to tell the organizers on time but got lucky in the end. I managed to give my ID to the security guy after 5 attempts, a record! Another friendly security guy filling up his water bottle at the dispenser kindly told me you were not aloud to fill your bottle. Training my problem-solving skills for tomorrow, I filled several glasses and filled my water bottle with them. When everyone had got through the security check-in, we got into the building. Unfortunately, the entrance wasn’t an elevator, as someone thought, but we did get a private lift operator to push the buttons. We were told to always stay with a leader so that we didn’t get lost (not a big chance of that with so much CEOI people), but not everyone managed, so we got to play Find Elias™ again. While searching, we found something else: free audio guides! We weren’t very interested, but we took some anyways for the obvious reason. And promptly set off an alarm as we went near the toilet where Elias had disappeared.

This is for the dome, not the toilet

—Security guard.

From the top of the dome, we could see the Swiss embassy (apart from Johannes who needed 10 minutes to find it). Back on the roof, we took pictures of 2 of the 3 symmetric permutations of t-shirt colours and decided to do the third one downstairs (we forgot [5]). The orgas told us to get, I quote, “done”. The file to get to the elevator had left a lot of space on the side, so Benji and I filled it. As you may have noticed, we felt very gracious today, and offered to help transport the exams which had just been printed but got refused promptly.

Our next stop was the Biergarten, where we shooed some groups away who sat at our reserved places. Johannes made a tentative guess we wouldn’t be finished by 6 pm (astoundingly, he was right). We discussed the twin prime conjecture and solved it to 50 % (according to our guide understanding the problem is half the work), and the strategy to apply if we got the task at 9 pm (only on a highly theoretical level). Jovian also commented that wasps only exist in Berlin. Then, our trauma from the morning repeated itself, as our leaders left us again! This time, their excuse was that they had to translate the tasks.

As they had taken the cool bus for themselves, we had to get into the lame one (at least it had working air conditioning). We played a Tichu, which could also be called a massacre, as Elias and I won 620 : -120 with 3 successful Doppelsiegs. We got to play Find Elias™ for the third time when walking to the youth hostel but found him quite quickly this time because of all the training we had had during the day. The orgas had trouble keeping up with us as we walked faster then them (I admit it, sometimes also in the wrong direction).

We then got to bed early. Naa, actually not happening, I had to write this blogpost. At least I found out I could use Special Styles [6]

“Ai hop zu licet zis progressive plogpost», as our guide would say.

P.S. For Saturday: Not fair you stole the flag, Benji, I did all the work!

[1]Word: This language may be offensive to your reader [2]
[2]Rendering the footnotes is up to our leaders
[3]It seems to the writer that being early everywhere may have nothing to do with the Swiss team, but actually is the making of our local guide
[4]This vision of events is not shared by the author nor the SOI organisation
[5]Big surprise there
[6]4 Gud Stuf!

Thursday, 17.08.2023 (Elias)

Today was the second contest day, so we had to get up at 7 o’clock again. After eating breakfast at the youth hostel, we walked to the contest hall again. This time we were joined by the Czech team as their guide didn’t have time in the morning. Then about 15 minutes after we arrived at the university, we started the contest. The tasks were hard again but still fun to solve. The second day went worse than the first day for me but I still managed to keep my bronze medal. Yaël did much better than me and even managed to get a full score, so he also snagged a bronze medal. After the contest we went to eat lunch, schnitzel with potatoes. Then we went back to the contest hall for one hour to do the analysis session. When leaving, we noticed that one of the leaders had left their room key in the contest hall, so we decided to prank them a little. We gave the key to Katharina, who wanted to play cards with the leaders in the evening. She promised to record their reaction when they realized they couldn’t get into their room. In the afternoon everyone from CEOI met for game night. I played Codenames and Wizard with some of the guides and participants from other countries. For dinner there was a grill setup and some local people made yummy food for us. After dinner we socialized some more and then went back to the youth hostel. At around midnight we got two messages in the CEOI group chat from Benjamin, first asking whether we had seen his key and then twenty minutes later that we were very funny. :)

Friday, 18.08.2023 (Andrej)

Photo with the two medals.

The official photo with our two Bronze medals. Top row: Otto von Guericke. Middle row: Benjamin, Duck Vader, Johannes. Bottom row: Andrej, Yaël, Elias, Jovian.

Today we were allowed to wake up a bit later than usual, which however was still not enough sleep after playing Tichu until midnight. The leaders were obviously nowhere to be seen. This morning we had a workshop about “Design Thinking”. We had to think about how we’d like to live in the future and for that we had to invent a persona. We (not at all because of us lacking inspiration) dressed a glorious portrait of our great Duck Vader, his goals, frustrations and biography in 2040. The leaders, surprisingly, showed life signs on WhatsApp around 11am. We found them about 5 minutes after entering the Mensa, which was a great achievement. After lunch, our local guide gave us a tour of the Magdeburg University library, which had way too many interesting books, far from enough time to read them, and a confusing architecture (supposed to look like stacked books from the outside). Then, after such a long time in Otto City, we went to see the two Otto hemispheres to rule them all (there are a ton of replicas lying around in the city) inside the Physics building. The building had the oldest room of the university (actually only ~20 years old), where Benjamin and our duck gave a lecture on balanced binary trees. While we walked to the tram station Johannes bought a maths riddle book for 50 cents (he seemed quite happy about it) in front of a bookstore. After buying a lot of postcards and getting all the t-shirts requested by our team leader we went back to the city hall where the closing ceremony took place. Once inside, we finally made good use of our chocolate, which we threw at gave to the other delegations, until the chief guide told us to stop that the chocolate was amazing.

Did I already write something about German people speaking English? Sachsen-Anhalt Minister of Education: “I can’t speak English, but I will try for you.”. Oh no. After quite a lot of speeches (with widely varying levels of English), thanks (three people received plushies), and a musical interlude, the interesting part (medals) finally started. Elias and Yaël both got bronze medals, with 190 and 225 points. The reader can guess as an exercise from which country the first place winner came (hint: that delegation got 2 gold medals). At the end of the ceremony, the flag was waiting just in front of us, so we stole it borrowed it to take some pictures. We proceeded to construct almost all the possible permutations of t-shirts, participants, leaders and flags in front of Otto von Guericke, who for some reason had a duck sitting on his foot the whole time. We then had a farewell dinner outside of the university, where the author of this blog was terribly unsuccessful at Tichu (losing about 1000 to 200) (may or may not be correlated with the presence of Yaël in the other team). After solving a few riddles about mice wearing colorful hats we played Kubb for quite a while, and after a final Find EliasTM we escaped the campus just on time before a group dance.

Saturday, 19.08.2023 (Jovian)

Saturday was the last day of the CEOI. After a long farewell party the night before, we were finally able to sleep in a little bit. At roughly 8:15am we all woke up and packed our belongings, ate our daily breakfast then headed down to the reception to walk to the train station for the long ride home. There was a 10:03 train to Hanover to catch; we easily arrived on time (surprisingly, it was not delayed) and enjoyed the hour-long trip to Hanover. The main activity of interest (or lack thereof) was writing on some Magdeburger postcards that had been purchased the day before, the recipients being SOI organizers chosen by us. People seemed slightly confused as to what was to be written, but overall it certainly felt refreshing to be able to sit back and chill after five days of very rigidly (and competently) planned activities. Soon after, we got off at Hanover Hbf and we were informed that the “ICE” train, which would be taking us to Basel, was delayed by five minutes. Compared to the 35-minute delay that we had faced when travelling in the other direction six days prior, this inconvenience felt minor and routine. With twenty minutes to spare, various participants made a quick trip to the station building to purchase lunch. (I did not, for I had already bought mine back at Magdeburg.) They returned gradually to the platform in anticipation of the intercity train. It arrived, and the leader and the three participants boarded the vehicle. The observant among you will notice that three is strictly less than four, and that one is strictly less than two. Indeed, we had strictly fewer people than necessary, because Benjamin and Andrej were still busy obtaining food. Benjamin sprinted back to the platform just as the train was starting up again, but ultimately was unable to enter the train. Andrej was nowhere to be seen. All of a sudden the mood turned from mostly bored and/or tired to anxious. The four who were on the train researched potential connections and attempted to find ways to resolve the situation. The two options were either riding the train all the way down to Switzerland (and thus home) or getting off at the next station (Göttingen) and waiting for the missing leader and participant there. Ultimately, we chose to stay on the train (for various reasons) and were soon joined by a contestant from the German team to play card games for a little while (four hours specifically). We reached Basel and we each went our own ways. Thus concluded the 30th Central European Olympiad in Informatics hosted in Magdeburg, Germany. Hopefully, we all qualify for the IOI next year. ;)