Hello everyone!

Codeforces round #165 will start today at 19:30 in Moscow time. It will be a round held in both divisions, the first one after a long two-week break for Div I participants. :)

This time the problems were prepared by me, Evgeny Vihrov (gen), and Krisjanis Prusis (cfk). Apart from competing together in ACM ICPC this year, we are also colleagues in a project that involves much algorithmic thinking. Actually, some of the contest problems were born during the work on this project.

In this contest you will get to know a legendary hero Emuskald of many talents and help him complete his ingenious ideas. The problems cover a multitude of algorithmic concepts, so as always we hope that each participant will find a problem that matches his taste.

Big thanks to Gerald Agapov (Gerald) for help during the preparation of this contest, to Maria Belova (Delinur) for problem statement translation and also to Mikhail Mirzayanov (MikeMirzayanov) for the excellent contest-making platform for Codeforces — Polygon.

We wish you an exciting round!

UPD1: Score distribution:

DivII: 500 1500 1500 2000 2500

DivI: 500 1000 1500 2000 2500

UPD2: Congratulations to the winners!

Div I

1. PavelKunyavskiy
2. Egor
3. tourist
4. rng_58
5. tomasz.kociumaka

Div II

1. woxihuanni
2. mnbvmar
3. QLSpirit_011
4. PraveenDhinwa
5. leviathan

UPD3: Tutorial is available.

Hello everyone!

The Codeforces Round #164 for Div.2 participants will start in several hours. Traditionally, the other participants can take part out of competition.

The hero of today's problems is Manao, which has been straining Georgian fellow programmers' minds for several years already. He made it to Codeforces pages thanks to Gerald and Delinur, who have assisted me in round preparation. The problems were also tested by Seyaua, sdya and Aksenov239.

The scoring system will be a little unusual: 500-1000-1500-2500-2500.

Good luck :)

UPD: The contest is over, congratulations to the winners:

1. first_love

2. dianbei_10

3. yefllower

4. dpij

5. cenbo

You can find the tutorial here.

Hello everybody)

Today is coming regular Codeforces round #163 for Div.2 participants. Traditionally the others can take part out of the competition.

The problems were prepared by authors: Rakhov Artem (RAD), Kudryashov Igor (Igor_Kudryashov), Pavel Kholkin (HolkinPV) and Gerald Agapov (Gerald). Traditionally thanks to Michael Mirzayanov (MikeMirzayanov) for Codeforces system and Mary Belova (Delinur) for translating the problems.

UPD: It is decided to use dynamic scoring system. The problems will be sorted from low difficulty to high by authors' opinion.

We wish everyone good luck and high rating)

UPD2: the contest is over, hope you enjoy it)

Congratulations to winners:

1) Aharon

2) marcoskwkm

3) ChaosLogic

4) Imsbuno

5) Conny

UPD3: the editorial can be found here)

Hello everyone,

I'd like to invite everyone to participate in a 5-hours Gym contest (both teams and individual participants can join) which will be held this Thursday, January 24th at 04:00 PM MSK (GMT+4), check for other time zones here: http://timeanddate.com/worldclock/fixedtime.html?day=24&month=1&year=2013&hour=16&min=0&sec=0&p1=166 (The registration will be opened 6 hours before the contest)

We will use the problems from the last ACM Arab Collegiate Programming Contest 2012 (English statements only), and the actual contest scoreboard will be merged into the Gym's scoreboard. Please don't participate if you already solved or read the problems. Hopefully the problems will be interesting for both Div1 and Div2 coders.

We encourage you to participate in teams to simulate the actual contest.

I'd like to mention that we used Polygon to prepare the problems for the actual contest, which is an amazing system and helped us a lot. Many thanks to Mike Mirzayanov and the whole team.

Edit 1: The registration is opened now, you can register here: http://mirror.codeforces.com/gyms

Thanks, Ahmed Aly

Hello!

I'm Squirrel Liss. I became the hero of today's contest. The writers of the contest are snuke, hogloid, DEGwer, and rng_58. I'd like to thank Gerald for helping preparation, Delinur for translation, and MikeMirzayanov for the Codeforces system. The point values will be standard: 500-1000-1500-2000-2500 for both divisions.

I will encounter many difficulties about stones, nuts, and sequences... Please help me!

Since 07:30 PM MSK is late here, the contest will be moved to 05:00 PM MSK. Please check the schedule in your time zone in timeanddate.com: http://timeanddate.com/worldclock/fixedtime.html?iso=20130120T22&p1=248&ah=2

UPD: Announced the detail of the contest.

The top five contestants in div1 were:

• 1: Petr
• 2: AleX
• 3: scott_wu
• 4: Zhukov_Dmitry
• 5: al13n

And in div2:

• 1: kesongyu
• 2: Moor
• 3: Qwaz
• 4: tsunayoshi
• 5: step5

Congratulations!

Also congratulations al13n and Komaki for solving div1 E problem.

The authors were

• D2 A: rng_58
• D2 B: snuke
• D1 A/D2 C: DEGwer
• D1 B/D2 D: DEGwer
• D1 C/D2 E: hogloid
• D1 D: rng_58
• D1 E: snuke

UPD: Tutorial was added here.

Hello everybody)

Today is coming regular Codeforces round #161 for Div.2 participants. Traditionally the others can take part out of the competition.

The problems were prepared by authors: Pavel Kholkin (HolkinPV), Nikolay Kuznetsov (NALP) and Gerald Agapov (Gerald). Traditionally thanks to Michael Mirzayanov (MikeMirzayanov) for Codeforces system and Mary Belova (Delinur) for translating the problems. Also thanks to Rakhov Artem (RAD) and Vitaly Aksenov (Aksenov239) for their help.

UPD: Today it is decided to use dynamic scoring system. But the problems will be sorted from low difficulty to high by authors' opinion!

We wish everyone good luck, successful hacks and high rating!

UPD2: the contest is over) hope you enoy it

Congratulations to winners:

1) poao900
2) persianpars
3) Sert
4) valentin.harsan10
5) MeinKraft

UPD3: the tutorial is published, you can find it here

Hello everyone!

Codeforces Round #160 will take place on Sunday, January 13th at 19:30 MSK. This is my third Codeforces round and I hope not the last.

I'd like to thank Seyaua, sdya and Gerald for helping me to prepare the round. Special thanks to Delinur for translation of all problem statements into English.

Problems’ point values will be standard in both divisions.

I strongly recommend you to read ALL the problems.

Gl & hf ! :)

Contest is over, I hope it was interesting for you :)

Congratulations to div1 winners:
1). PavelKunyavskiy
2). Dmitry_Egorov
3). Nerevar
4). Egor
4). gawry

and div2 winners:
1). Pad
2). nirvanafreak
3). pablobce

You can view tutorial here.

Codeforces Testing Round 5 starts on Jan. 12, 2013, 15:00 (UTC). Our goal is to test the platform after recent improvements. You may notice that we've improved real realtime status. You may visit (problemset status)(http://mirror.codeforces.com/problemset/status) and find that it updates automatically without page reloadings. It uses modern web realtime technologies like websockets and so on. For sure, no server polling!

Also we've updated server software and built Codeforces with Java 7.

I invite you to take part in the round. It will be Div. 2 + unofficials from Div. 1. It will contain three obsolescent problems. But I think it will be interesting for many of you. The problems contain very weak pretests to force more hacks. It will be unrated round.

Many thanks to participants!

P.S. As it is testing round, we do not guarantee stable work and so on.

Hi to all!

A few hours later you're lucky to participate in Codeforces Round #159 for Div.2 participants, but traditionally the others can take part out of the competition. It has been prepared by me (NALP), Ivan Fefer (Fefer_Ivan), Pavel Holkin (HolkinPV), Vitaly Aksenov (Aksenov239) and Gerald Agapov (Gerald). Also we express thanks to Mary Belova (Delinur) and Mike Mirzayanov (MikeMirzayanov).

Traditionally I wish good luck, accepted solutions and successful hacking attempts for you!

UPD: Today it is decided to use dynamic scoring system. But the problems will be sorted from low difficulty to high by authors' opinion!

UPD: The contest finishes, congratulations to the winners!

1.GreatEagle

2.CarlyPlus

3.Dakurels

4.ytqiaqia

5.SuccessfulHackingAttempt

Calendar: (c) 2011 Anatoly Rr

The Codeforces project wishes all its users a successful New Year. May all your handles change the colors only towards red, may all your solutions go well without debugging and may you enjoy many times the coveted Accepted at each contest! We wish you good luck in everything you do next year — isn't that great to have luck on your side!

Traditionally, the Codeforces enables the users to change their handles. Note that this is a one-time change and you won't be able to return to the previous handle. Analyze all 'for' and 'against' carefully as the handle is what you are going to be often called by the numerous participants of the Codeforces contests.

We've got more good news. We've decided to increase the list of people who can get the role of the 'coach' in the Codeforces project::training. Check out all those training sessions! Now this role can be given to those who:

• have got the red color handle (i.e. the rating of at least 2200),
• have got the orange color handle, have participated in a Codeforces official contest not more than six months ago and have taken part in at least 30 rated Codeforces contests).

This innovation is going to increase the number of potential coaches roughly by two!

And the last, but not the least detail. Now we can increase the authors' fees for preparing contests. That will hopefully give a little motivation to those who can make an interesting round. In 2013 the authors' fees is:

• preparing a Div.1 + Div.2 round (USD): 250 + 50*,
• preparing a Div.2 round (USD): 100 + 50*.

(We use fixed rate USD = 40 rubles, so actual payment may differ slightly). The sums with asterisks are the extra bonuses the author gets for 'good quality'. The author receives the bonus if he worked without jeopardising the deadlines for preparations and the round went without any major problems with the statements (no additional major notices, fixes in solutions/tests/checkers/validators etc.).

We hope to work with authors efficiently in 2013, we hope that our best participants will generously dazzle the community with interesting contests! For more information or to organize a context, please message Codeforces problem coordinator Gerald (Gerald Agapov).

Happy New Year!