Hello Everyone!

Indonesia will hold National Olympiad in Informatics next week (May 19th — May 21th 2015) in Yogyakarta, Indonesia. The contest consists of three separated contests:

- Day 0 (Practice Contest): Tuesday, May 19th 15.00 — 17.00 (UTC +7)
- Day 1: Wednesday, May 20th 08.30 — 13.30 (UTC +7)
- Day 2: Thursday, May 21th 08.30 — 13.30 (UTC +7)

We want everyone to try solving the problems by participating the Open Contest! The Open Contest will be held in https://competition.ia-toki.org/.

There will be three different contests, one for each day. You may participate them separately (e.g. only participate in Day 1 and Day 2, but not in Day 0), but we expect you to join them all. All of them are virtual contests, which means that you can start anytime according to your preferred time, but still within the time limit. The Open Contest will start after a delay from the real contest. Here are the schedule and details for the Open Contest:

- Day 0: Tuesday, May 19th 15.30 — Wednesday, May 20th 09.00. You may choose any 2-hours range within the given time. Registration closes on Wednesday, 10.00. Register here.
- Day 1: Wednesday, May 20th 10.00 — Thursday, May 21st 10.00. You may choose any 5-hours range within the given time.
**Registration closes on Thursday, 09.00**. Register here. - Day 2: Thursday, May 21st 10.00 — Friday, May 22nd 10.00. You may choose any 5-hours range within the given time.
**Registration closes on Friday, 09.00**. Register here.

All times are in UTC +7.

Several notes:

- No medals/certificates will be awarded to Open Contest participants.
- Each contest will have 3-4 IOI-styled problems.
- Problem statements will be provided in English and Indonesia.
**UPD**There is a submission limit of**20**for each problem (instead of 30).**UPD**We extend the registration time until an hour before the contest ends.

**UPD**: Thanks for all people who participated in the Open Contest, despite of the euphoria of the World Finals.

**UPD**: The results are now published! You may find them here: https://osn2015.ia-toki.org/, inside the "Open OSN International" tab. A little summary:

- There are 34 people in this category who at least submit something. The registrants who didn't submit anything will not appear in the scoreboard.
- 5 of them get full 600 points.

Once again, thanks for your participation!

Indonesian National Olympiad in Informatics Committee

What is the expected difficulty of tasks, compared to IOI?

We expect them to be easier than IOI, for it is only national contest. The last year's hardest problem was somewhat proportional to the medium level problems of IOI. But we are trying to increase the difficulty each year.

Unfortunately I can't participate during these times. will you publish the test cases afterwards? Or open the contests for practice?

"

all of them are virtual contests, which means that you can start anytime according to your preferred time"UPD: I'm sorry. I've understood your question wrongly. I don't know if it will be open.

Sorry, unfortunately no. But we're in the process of creating a problem archive web application. Stay tuned for the next few weeks!

Wait, you won't publish a few archives, but try to make an entire application for this? Not to mention there are problem archives all around (like CF Gym) and you could just add it to one?

That's not very efficient.

I could not find a way to enter the contest(day 1). Am i the only one?

Probably because the registration was closed several hours ago. We have just extended the registration time until 9 AM UTC+7 tomorrow. You may enter (by registering first) the contest now. If any problem occurs, please let me know.

Will you publish results?

Yes, we are now compiling the results from Day 1 and 2, and it will be out tomorrow.

Test data plz

For problem 2A is there a solution independent of N? I thought of passing on all the times and determining whether it is possible for any two ducks moving in opposite direction to meet or distance is.one and at the end relax from every time to other times by bfs increasing distance by two and don't forget to check whether two moving in same direcetion is smaller the question is, is it possible to make that calculation for large value of N?

Results are wrong. My 2A problem was 100 but it shows like I did not submit anything.

Oh sorry, it should be fixed by now