Arpa's blog

IOI vs CF performance: 2024 Edition
By Arpa, history, 6 weeks ago, In English
CF ratings are unrelated to your IOI results. CF contests differ significantly from IOI contests.

❌ Wrong!

A higher CF rating, with a gap of at least 100, correlates with an 87% chance of achieving a better placement at IOI. In fact, the relationship between IOI placement and CF rating is strongly connected. The Pierson Correlation Coefficient for these two factors is -0.83.


Correlation between CF rating and IOI placement

❗ What is that outlier participant on the top-right? He is Jiyu Shen (PubabaOnO), with CF rating of 3000+, but it seems that he was unable to attend the contest 💔

Here are the statistics on CF ratings for each medal:

Medal Minimum Median
🥇 2029 2469
🥈 1501 2274
🥉 1637 2082

Additionally, I've discovered an interesting correlation: participants' ratings one year before IOI also correlate with their final ranks. By the way, some participants showed remarkable jumps in their ratings during that one-year period. Specifically, there were 4 participants with 1000+ growth in CF rating!



Correlation between CF rating a year before IOI and IOI placement

Based on this insight, I’ve trained a model that can predict your placement at IOI. If you’re curious about your predicted placement for IOI 2025, leave a comment! Note that as time passes, the model can determine your place more accurately. So you may comment again 6 months later to see the updated prediction.

Check out the similar blog for IOI 2019 here.

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6 weeks ago, # |
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What I find quite interesting is that difference between gold and bronze is only 400 points. Not a small amount, but it's by no means a large gap. I'm interested if something similar is at their OI level?

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    6 weeks ago, # ^ |
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    I do believe being Red from CM is much harder than being CM from nothing. 7 out of 100 total CF user is CM, 4 out of 100 (+1900) CF user is Red.

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    6 weeks ago, # ^ |
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    Reaching 2400 from 2000 is several times harder than reaching 2000 from 1600. For most people, it's nearly impossible. That's why the significance of a 400-point difference depends heavily on the rating range.

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6 weeks ago, # |
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just a small detail, I believe Jiyu Shen was disqualified, but his performance was top 5 if I recall correctly, so it does still support your point

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    6 weeks ago, # ^ |
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    Thanks for pointing that out. I wasn't aware of it. I noticed his scoresheet was empty and assumed it was due to his absence.

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    6 weeks ago, # ^ |
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    No he wasn't top 5.

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6 weeks ago, # |
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"unable to participate" kekw, how much did you get paid

i guess he couldn't do it without a phone, sad to see the rewriting of the history going underway

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6 weeks ago, # |
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Please predict my placement. Lol, hoping for at least bronze :sob:

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6 weeks ago, # |
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What if you remove everyone that hasn't done, say, 5 rated contest in the last 6 months? Otherwise, your data contains ratings that probably aren't "true".

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    6 weeks ago, # ^ |
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    I only included people who participated in at least a contest. I did what you say right now, and correlation got stronger just by 0.02 (=-0.84).

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      6 weeks ago, # ^ |
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      I'm a bit confused about what is going on your plots with the rating distribution of the gold medalists. For example, it looks like only in this last plot is there someone with rating just below 2000 in gold. But this plot should simply contain a subset of the data from the other plots. So that doesn't make any sense.

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        6 weeks ago, # ^ |
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        Thanks for reporting. There was a bug in calculating this plot. After recalculation, it added just 0.01 to the correlation. Here is the correct one.

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6 weeks ago, # |
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Whats mine im curious

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    6 weeks ago, # ^ |
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    115! But personally I think you can easily reach silver.

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    6 weeks ago, # ^ |
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    Nice pfp brother

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6 weeks ago, # |
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mine?

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    6 weeks ago, # ^ |
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    107, but your account is quite fresh. I think you can easily reach silver.

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6 weeks ago, # |
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Predict my placement too please

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    6 weeks ago, # ^ |
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    95, on the cut of silver and bronze.

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6 weeks ago, # |
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Can you predict mine placement?

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6 weeks ago, # |
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While the data does indicate correlation between CF rating and IOI result, I disagree that it's wrong to say "CF contests differ significantly from IOI contests". It is a very different style of contest: 2-3 hours and you must solve as quick as possible vs. 5 hours, no penalty for resubmission, subtasks etc.

Of course, being good at one will probably mean you are good at the other, since the core problem-solving skills are applicable to both. But personally I struggle to consistently perform on div 1s due to silly mistakes, running out of time or getting stuck on one problem for too long and having too high penalty even if I solve later problems. Meanwhile in an OI contest none of those factors are nearly as significant, and I had a very strong performance at IOI this year. Of course maybe this just means I need to train more on Codeforces...

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6 weeks ago, # |
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I am interested!

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6 weeks ago, # |
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Can you predict mine

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    6 weeks ago, # ^ |
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    135

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      6 weeks ago, # ^ |
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      I actually got 199 :(

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        6 weeks ago, # ^ |
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        Please note: The model doesn't predict the placement in IOI 2024, it also take into account the growth you'll have during the time you have until IOI 2025.

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          6 weeks ago, # ^ |
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          Oh I didn't notice. That's nice. I also think that my rating actually says that I should rank better than I actually did in IOI

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6 weeks ago, # |
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Can you predict mine please

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6 weeks ago, # |
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Predict mine please

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6 weeks ago, # |
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Can you predict mine please

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6 weeks ago, # |
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Can you predict mine please ?

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6 weeks ago, # |
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I don't even have time to compete in CF rounds though!!!!!

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6 weeks ago, # |
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Could you please predict mine?

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6 weeks ago, # |
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would like to know mine over the course of time. grinding for expert rn

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6 weeks ago, # |
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Mine plzzz

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6 weeks ago, # |
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please predict mine

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6 weeks ago, # |
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mine

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6 weeks ago, # |
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so Orange or higher in cf = almost guaranteed IOI medalist

quite interesting, cf rating is so much valuable than what I thought

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    5 weeks ago, # ^ |
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    cf rating is so much valuable than what I thought

    It's not. It's just that when reahing 2100+ level (preferably, from div1, reaching master from one lucky div2 contest isn't what i really mean...) you have enough skill/common sense, call it whatever you want, to be able to get medal even in you worst performance case. That's why it's (almost) always guaranteed IOI medal. You can't describe any medal with certain required cf rating (there is an actual CM gold medalist this year as well as there are many GMs in silver/bronze), but you can give such a "lower bound" for skill level (which div1 masters characterize pretty well). Everything else is mostly luck.

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    5 weeks ago, # ^ |
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    the classic "correlation does not imply causation".

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6 weeks ago, # |
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How does the fit look if you only look at silver and golds? I feel like getting bronze on IOI is fairly easy once you have some solid CP base, so it probably correlates with higher rating on any website. For the distinction of silver vs gold, though, it becomes a lot more critical to practice the format and the problem styles, so something like CF shouldn't be too predictive (except maybe in the 3000+ rating, which just signifies insane abilities overall).

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    6 weeks ago, # ^ |
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    a lot of it is also just random noise due to ioi being only a 2 day event. Even previous IOI results won't correlate with future IOI results. For example, consider https://stats.ioinformatics.org/people/1144

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      6 weeks ago, # ^ |
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      I'm well aware that there's a lot of variation (me), but still might be somewhat interesting to see the correlation. But you're probably right that there's too much noise to get anything useful from this one year.

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6 weeks ago, # |
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Could you predict mine, please?

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6 weeks ago, # |
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What about mine?

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6 weeks ago, # |
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Can you predict mine please?

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6 weeks ago, # |
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Hope you to calculate Guo Yuchong,Huang Luotian and Shen Jiyu's real score,not the score after they were punished to get a more precise answer.

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6 weeks ago, # |
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What's your prediction about me?

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6 weeks ago, # |
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Mine?

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6 weeks ago, # |
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mine ?

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    6 weeks ago, # ^ |
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    I don't think my model can predict correctly for unrated account. Go participate in at least 5 contests and come back.

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6 weeks ago, # |
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mine?

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6 weeks ago, # |
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Mine please :)

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6 weeks ago, # |
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CF contests are ICPC styling which is harder than IOI. Hence, a high CF rating means higher performance in IOI. Nice blog <3

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6 weeks ago, # |
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Can you predict mine

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6 weeks ago, # |
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Can you predict my placement?

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6 weeks ago, # |
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Can you predict mine?

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6 weeks ago, # |
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Which is my prediction?

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6 weeks ago, # |
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Which is my prediction?

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6 weeks ago, # |
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can you help me check my predictions?

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6 weeks ago, # |
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please predict mine

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6 weeks ago, # |
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Can you predict mine please

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6 weeks ago, # |
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Curious, Arpa:

What does this analysis (I mean the predictions part) look for other IOIs? [Since you mentioned you can predict performance in IOI 2025, that would probably mean older accounts get an "unfair advantage" due to more time to practice?]

Also, this analysis has been done for CF ratings at the time of IOI, right? [Which may not be the max rating of the said account till IOI time]

I wonder how the graphs / plots look if you consider the max ratings?

Also, just for fun: can you predict mine please?

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    5 weeks ago, # ^ |
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    Do you mean in IOI 2026+? I think that there is no accurate prediction.

    Here is the plot for max rating, but note that it shows a bit less correlation with the IOI result (Pierson Coefficient is 0.80). It seems very similar.

    The last contest you participated in is very old and can't be used for prediction.

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6 weeks ago, # |
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Can you predict mine?

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5 weeks ago, # |
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Can you tell us how you predict placement of people ? Is that possible to make a website that can predict placement of users by their handle ?

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    5 weeks ago, # ^ |
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    Is that possible to make a website that can predict placement of users by their handle ?

    I'm thinking about that.

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5 weeks ago, # |
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What about mine?

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5 weeks ago, # |
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Can you please predict mine?

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5 weeks ago, # |
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Can you predict mine please?

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5 weeks ago, # |
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I think the following adjustments would make it more accurate:

1) filter to those who have participated in at least six contests, because otherwise their rating would be downwardly biased due to the CF base rating of 1400 being credited over six rounds, and

2) filter to those who joined at least once over the past six months

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5 weeks ago, # |
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me tooooo....please

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5 weeks ago, # |
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Can you predict mine?

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    5 weeks ago, # ^ |
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    90

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      5 weeks ago, # ^ |
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      Close, I am actually 89th.

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        5 weeks ago, # ^ |
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        Please note: The model doesn't predict the placement in IOI 2024, it also take into account the growth you'll have during the time you have until IOI 2025.

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5 weeks ago, # |
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Could you calculate it after 2100? I am actively thinking about leaving codeforces

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    5 weeks ago, # ^ |
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    2100 is where the fun begins

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      5 weeks ago, # ^ |
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      Lmao I agree. But sadly olympiads aint no fun and implementation and algorithm heavy

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5 weeks ago, # |
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It's funny that what used to be people asking for their future rating to be predicted turned into people asking for a prediction of their expected IOI ranking XD

Now on a more serious note, great job for your work, now as a follow up, it would be interesting to see whether this metric remained the same over the years and how can these results reflect a country's improvement or downfall in terms of future IOI performances and what can we learn from this.

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5 weeks ago, # |
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Whats mine im curious

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5 weeks ago, # |
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Can you predict mine please.

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5 weeks ago, # |
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Can you predict mine please

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