From 10th to 16th May, Ukrainian Selection Camp for the IOI (International Olympiad in Informatics), BOI (Balkan Olympiad in Informatics) was held in Wrocław, Poland.

Thanks to University of Wrocław and gawry for the second time for help in organising the selections!

We are very grateful to Sergey Kolodyazhnyy for creating powerful online judge Eolymp.

Also, I would like to thank oleh1421 and kostia244 for preparing amazing problems. Maryna, Ilona and Melissa_14 for looking after the participants and Federation of Olympic Programming of Ukraine presented by arsijo for coordinating the entire process.

So, on IOI Ukrainian Team will be represented by:

• Andrii Smutchak(xGaz_) — 2nd time at IOI(IOI 23 Silver), 0 attempts left
• Ihnat Zharikhin(Ignut) — 1st time at IOI, 0 attempts left
• Denys Tereshchenko(TheQuantiX) — 1st time at IOI, 0 attempts left
• Illia Permiakov(160cm) — 1st time at IOI, 0 attempts left

Left to right: Illia, Ihnat, Andrii, Denys

And on BOI Ukrainian Team will be represented by:

• Maksym Shvedchenko(Umanity) — 1st time at BOI, 1 attempt left
• Valerii Kovnatskyi(Triseedot) — 1st time at BOI, 0 attempts left
• Daria Perekopska(perekopska.d) — 1st time at BOI, 1 attempt left
• Kyrylo Redenskyi(Relex) — 1st time at BOI, 0 attempts left

Left to right: Maksym, Valerii, Daria, Kyrylo

As usual some photos of our delegation included =)

Good luck to them at the upcoming olympiads!

On May 19, at 16:00 UTC the second competition of the Eolymp Weekend Practice series will take place. Learn more on the competition website.

Format and Difficulty

Same as the first round, the competition is primarily aimed at improving practical skills. There will be 5 tasks of varying difficulty, the easiest of which can even be solved by beginners.

The scoring for each task being block-based (meaning points are awarded for each block of tests separately, and only if the solution passes all tests in the block). If there is a tie between two participants, the one whose last productive submission (i.e., a submission that added at least one point) was made earlier will be ranked higher in the leaderboard.

This series has a standard duration of two hours.

The statements will be available in the following languages: English, Ukrainian, Russian, Polish, German, French, Spanish, Azerbaijani.

Registration

You can register for the competition on its page.

Thanks a lot to:

• arsijo for coordinating the contest
• Sergey Kolodyazhnyy for creating Eolymp
• Umanity, Do_not_make_friends, Frus for authoring the problems
• peltorator, 160cm, TheQuantiX, Ignut, Geforgs, Fatonim_, Melissa_14 for testing the contest

Prizes

The top-10 participants of the competition, as well as 10 random participants from those who rank from 11th to 100th place, will receive prizes in the form of t-shirts. Please, note, that we have changed how prizes are awarded,

• We will send prizes for free to EU countries (with few exceptions), Ukraine and Azerbaijan. If you live in another country, we still may arrange delivery for you, but additional conditions and fees may apply.

• If you already got a T-Shirt in the first round, we will not send you another one, because it will be excatly the same.

Visit Frequently Asked Questions section to learn more.

UPD:

Congrats to the winners:

• VladProg
• wakaka
• Triseedot
• nfssdq
• andr1y
• Psiuk_Yurii
• xGaz_
• Valera_Grinenko
• Tahirliyev
• Wansur

Next Sunday, March 24, at 16:00 UTC the first competition of the Eolymp Weekend Practice series will take place.

Format and Difficulty

As the name suggests, this series of competitions is primarily aimed at improving practical skills. There will be 5 tasks of varying difficulty, the easiest of which can even be solved by beginners.

The distribution of points by tasks is 50-100-200-300-350, with scoring for each task being block-based (meaning points are awarded for each block of tests separately, and only if the solution passes all tests in the block). If there is a tie between two participants, the one whose last productive submission (i.e., a submission that added at least one point) was made earlier will be ranked higher in the leaderboard.

This series has a standard duration of two hours.

The statements will be available in the following languages: English, Ukrainian, Russian, Polish, German, French, Spanish, Azerbaijani.

Registration

You can register for the competition on its page.

Prizes

The top-10 participants of the competition, as well as 10 random participants from those who rank from 11th to 100th place, will receive prizes in the form of t-shirts. Please note that Eolymp currently sends prizes only to countries that are part of the Council of Europe.

Read more

UPD:

Congrats to the winners!:

1. andrey27sm

2. NK_

3. TheQuantiX

4. MAKMED1337

5. esomer

6. thenymphsofdelphi

7. huz_n

8. fuad27

9. Glauco

10. Sahib_

The editorial is available by the following links:

1. The Cubes
2. The Strings
3. Some Complex Formulas
4. Scared String!
5. Is This FFT?

Hello codeforces!

Recently in the problem I came across with this data structure, which can perform this operations:

• add element

• delete element

• return the maximal of it

with O(1) for query.

So the question is simple: is it exist?

Given an array of integers a (len(a) < 10^5, 1 <= a[i] <= 10^9).

There are q queries of two types:

In the first type, two numbers x (0 <= x < len(a)) and y (1 <= y <= 10^9) are given. You need to change the element of the array a at position x to y.

In the second type, two numbers l and r are given (0 <= l < len(a), 0 <= r < len(a), l < r). You need to find two different indices x1 and x2 belonging to the segment from l to r (inclusive) such that their greatest common divisor (GCD) is the largest possible among all pairs (output the GCD).

I know how to solve this problem with brute force O(qn^2), but I am personally interested in finding a solution with a better complexity (O(qlog(N))).