MikeMirzayanov's blog

By MikeMirzayanov, 9 years ago, translation, In English,
Welcome to the Codeforces Beta Round #6.

It will be good to see your feedback and impressions in the comments.

Wish you high rating,
MikeMirzayanov.

UPD. It seems the problem D has some tricky issues around judge solutions. Judge solutions will be fixed and the problem will be rejudged. If it will affect many participants, the contest will not be rated.

UPD 2. We have reduced constraints in the problem D and made rejudge. No solution passed tests. So the rejudge affected significantly only 4 participants, who solved it during the contest. But all of them increase their rating if we will count the contest as rated event. So we decided to make it rated and put problem with lowered constraints into the practice.

UPD 3. And by the way, the round tutorial is waiting for a volunteer. The tutorial should be in Russian and in English. It will be published on the homepage and later will be available via special link from the contest page.

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By MikeMirzayanov, 9 years ago, translation, In English,
Hello to everyone.

The latest news - now you are able to see the source code of the solution. During the contest you can view your own solutions only, but when the contest is finished you can view the solutions of any other participant. The table with the solutions is available via the problemset page, the solutions there are sorted by the program length. Pay attention, please, that you are free to change the sorting criteria using the option at the bottom of the table. 
There is another principle that gives you the chance to view the source codes of solved (during the contest or practice) solutions only. Personally, I regard the principle "everyone sees everything" as more suitable for our regular contests.  Am I right?

When you run a contest within your private community, you'll be able to set up your own principle for viewing solutions (or to switch off this function at all). But this functionality is under construction now. 

Wish you high rating,
MikeMirzayanov

UPD. Standings page is improved. You may double-click into a table cell (or use Ctrl+click) to view the submissions history.

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By MikeMirzayanov, 9 years ago, translation, In English,
Welcome and good luck on the round! 

I'd like to remind that if you have any questions on the problems, the best way to ask them is to use the web interface on the problems page. 

Later in the same post we will discuss the round. 

Wish you high rating,
MikeMirzayanov.

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Announcement of Codeforces Beta Round #5
 
 
 
 
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By MikeMirzayanov, 9 years ago, translation, In English,
Hello, everybody. 

At this point we have already decided on the date of Codeforces Beta Round#5: it's Saturday, March 20. The exact time is still unknown. I do want to find the best time suitable for most participants. Please, express your ideas in the comments - of course, you should not come up with the time that suits only you, but suggest the most suitable time for the majority.  

Wish you high rating,
MikeMirzayanov

UPD.  Thanks to everybody who wrote comments - I've read them all. The venture proved to be useful. Without your help, I wouldn't have been able to take into consideration all those factors which can affect the number of participants.  After much thought, I've made a decision to schedule the round for 19:00 (Moscow time) - I think this option is convenient for most users of the site. It does not mean that we will not experiment with time in future - we will try morning contests, but I can't promise about 5:00:).

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By MikeMirzayanov, 9 years ago, translation, In English,
I propose to discuss here the issues and troubles associated with Codeforces Beta Round #4.  On our side, we identified three difficulties: 
  • Slow judging - apologize for the large queue, to the next round, I assume significantly increase the speed of judging;
  • Runtime errors on Python solutions - apparently the decision they want to load some library, which is prohibited by security reasons;
  • Sometimes incorrect runtime errors - apparently the result of the antivirus on testing servers, they will be turned off on the next rounds
Also express your impressions about the round.

P.S. And by the way, the round tutorial is waiting for a volunteer. It is desirable that it will be one of the leaders of today's competition. The tutorial should be in Russian and in English. It will be published on the homepage and later will be available via special link from the contest page.

UPD. The ratings have been updated.
UPD 2. Thanks to KudryashovIA for his help in making contest.

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By MikeMirzayanov, 9 years ago, translation, In English,
In email notification (in Russian) I've made a typo. The phrase "It starts on March 12 (Friday), 2010, 12:00" should be read as "It starts on March 12 (Friday), 2010, 15:00".

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By MikeMirzayanov, 9 years ago, translation, In English,
I propose to discuss here all that concerns Codeforces Beta Round #3. Of course, during the competition it is forbidden to write anything about the solution of problems and similar things  

For the time of this contest, we turned off the chat server. This does not mean that it will not operate in future - I think it is a convenient and efficient way to communicate during the competition and you may expect it in the future.  

Also I'd like to announce Codeforces Beta Round #4, which will be held next week. It will be for participants from the second division (non-rated users or those having less than 1500 rating points). We will try not to delay Codeforces Beta Round #5, which will be opened for all. 

Wish you high rating,
MikeMirzayanov

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Announcement of Codeforces Beta Round #3
 
 
 
 
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By MikeMirzayanov, 9 years ago, translation, In English,

It seems everyone is in the know that Codeforces Beta Round#3 didn’t take place in the appointed time. Seemingly, it happened because of the increased popularity of the site, on the one hand, and some of our bugs, on the other. For sure, it’s a pity that things went in such a way. On the other part, if everything had failed during the contest, it would have been worse. The contest is rescheduled for Sunday, 15:00 (Moscow time). Please be sure to check here for the start time in your time zone: http://www.timeanddate.com/worldclock/fixedtime.html?&day=07&month=03&year=2010&hour=07&min=00&sec=0&p1=179

I’d like to remind you that the project is in Beta yet, and we’ll work on the problem and try to fix it.

Thanks for your understanding,
MikeMirzayanov

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By MikeMirzayanov, 9 years ago, translation, In English,

According to The November Revolution of Colors and Titles, the text below is not an actual and just a historical document.

Not so long ago a new rating system was introduced at Codeforces. To complete the picture I’ll tell you about our Table of Ranks.

From this moment on all the participants will be given ranks that reflect their skills and abilities at such a hard field as computer science and problem solving. Judging by the results of previous rounds you will gain (or lose, I hope it’s not your case) points. If you score big success, you are promoted to a higher rank. You can see the dependence between rating and ranks in the table below. Moreover each rank has its color, which is reflected in the table.

RatingRank
0-1199Recruit
1200-1349Corporal
1350-1499Sergeant
1500-1649Lieutenant
1650-1799Captain
1800-1999Major
2000-2199Lt. Colonel
2200-2399Colonel
2400-2699General
2700+Marshall

As you have already noticed: we have only three captains in our regiment: vepifanovgusakovRAVEman. But I’m sure, after Codeforces Beta Round#3 we’ll have a number of promotions.

Wish you high rating,
MikeMirzayanov

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By MikeMirzayanov, 9 years ago, translation, In English,
Codeforces will be unavailable for up to 6 hours while we upgrade our infrastructure (March 3, 4PM - 10PM). Thank you for your understanding.

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By MikeMirzayanov, 9 years ago, translation, In English,

As some users have already noticed - contest rating has been added to Codeforces. For now it is in beta too, but it looks very adequate. Here's how it is calculated.

Each person is characterized by their rating, the number R. If person A's rating is RA, and person B's is equal to RB, then the formula


gives the probability that A will get a higher position than B in the round final standings. By the way, here everything is very close to the Elo rating.

Before updating your rating after the end of the round, for each participant his seed is calculated, that is the place that the participant is expected to take in this competition. Thus, two things are known for each participant - his seed (the expected place) and rank (the actual place). Depending on the difference between these two values, your rating increases or decreases. If the difference is higher, your rating changes more.

There are a few technical points:

  • if it is the first contest for a participant, his seed is calculated as 1 + n / 2, where n is the total number of participants in the round;
  • changes in the ranking of contestants are multiplied by a correction factor such that allows the sum of ratings of the participants to remain unchanged (before and after the round).

As at TopCoder all users are divided into two divisions: the first (rating over 1500 1650) and the second (rating_ not more than 1500 1650). Not rated users fall into the second division automatically.

Wish you high rating,  

MikeMirzayanov

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By MikeMirzayanov, 9 years ago, translation, In English,

Thank you all for participating in Codeforces Beta Round # 2. I hope you enjoyed it. You may discuss the problems and system in comments. Please express your opinion, especially if you notice any inappropriate behavior. And as always, I will read with interest the suggestions for improvement.

Congratulations to the three leaders: RAVEman, GarnetCrow and ivan.popelyshev!

See you at Codeforces Beta Round # 3.

P.S. And by the way, the round tutorial is waiting for a volunteer. It is desirable that it will be one of the leaders of today's competition. The tutorial should be in Russian and in English. It will be published on the homepage and later will be available via special link from the contest page.

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Announcement of Codeforces Beta Round #2
 
 
 
 
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By MikeMirzayanov, 9 years ago, translation, In English,
In this topic I would like to raise issues around Codeforces Beta Round # 1. What did you like? What is not liked? What seemed uncomfortable? What can be changed to make participation more comfortable?  I wonder your opinion on contest web-interface. 

Please do not write about access the site with the address http://codeforces.com/ (I recommended to use http://codeforces.com:8081/). I guess the problem is around of Apache Virtual Hosts + AJP Connector. Something is configured incorrectly or doesn't work properly because , then it works so good. In short, I will correct. 

I'm waiting for your comments. And, of course, welcome to Codeforces Beta Round # 2. 

Also I would like to see someone who wants to write contest tutorial. This must be done in Russian and English languages. Of course you must solve the problem on either contest, or in the practice. If you have a desire to do it - write in comments. Your post will be published on the main page and later available on special link available from the contest page.

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Announcement of Codeforces Beta Round #1
 
 
 
 
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By MikeMirzayanov, 9 years ago, translation, In English,
 
 
 
 

By MikeMirzayanov, 9 years ago, translation, In English,

Later you'll be introduced to the rules of the Codeforces contests, which differ from those of ACM-ICPC, TopCoder, GCJ, and I hope they'll bring some difference to the world of programming competitions. Most of the official competitions will be carried out according to these rules, though there will be more traditional contests. For example, Codeforces Beta Round #1 will be carried out according to the familiar ACM-ICPC rules. For some time testing will be based on Windows, but things might change in future, fortunately, the system supports testing on different platforms, even within one contest.

At the present time the system is configured to support the following programming languages (the compilation and/or the launching line is shown for each language):

  1. GNU C++ 4
    g++.exe -static -DONLINE_JUDGE -lm -s -x c++ -Wl,--stack=268435456 -O2 -o {filename}.exe {file}

  2. GNU C++11 4
    g++.exe -static -DONLINE_JUDGE -lm -s -x c++ -Wl,--stack=268435456 -O2 -std=c++11 -D__USE_MINGW_ANSI_STDIO=0 -o {filename}.exe {file}

  3. GNU C 4
    gcc.exe -static -fno-optimize-sibling-calls -fno-strict-aliasing -DONLINE_JUDGE -fno-asm -lm -s -Wl,--stack=268435456 -O2 -o {filename}.exe {file}

  4. MS VS C++
    cl /W4 /F268435456 /EHsc /O2 /DONLINE_JUDGE {file}

  5. Free Pascal 2
    -n -O2 -Xs -Sgic -viwn -dONLINE_JUDGE -Cs67107839 -Mdelphi -XS {file} -o{filename}.exe

  6. Delphi 7
    dcc32 -Q -$M1048576,67107839 -DONLINE_JUDGE -cc {file}

  7. C# Mono 2
    dmcs -define:ONLINE_JUDGE -o+ -out:{filename}.exe {file}

  8. C# .NET
    csc.exe /o+ /d:ONLINE_JUDGE /r:System.Numerics.dll /out:{filename}.exe {file}

  9. Java 6, 7
    javac -cp ".;*" {file}
    и
    java.exe -Xmx512M -Xss64M -DONLINE_JUDGE=true -Duser.language=en -Duser.region=US -Duser.variant=US -jar %s

  10. Ruby
    ruby.exe %s

  11. Python 2, Python 3
    python.exe %s

  12. PHP 5
    php.exe -n -d ONLINE_JUDGE=true -d display_errors=Off -d error_reporting=0 %s

  13. Haskell GHC 7
    ghc --make -O %s

  14. D
    dmd -L/STACK:268435456 -version=ONLINE_JUDGE -O -release -inline -noboundscheck {file}

  15. OCaml
    ocamlopt nums.cmxa str.cmxa -pp camlp4o -unsafe -o {filename}.exe-ocaml {file}

  16. Scala
    As Java

  17. JavaScript V8
    d8 {file}

It is not guaranteed that all the problems will have solutions in all the given languages (it's especially about the scripting ones). Probably, I'll later introduce equalizing coefficients for the working time for some languages. A "plus" next to the version name means that the testing system can use older versions. If you have suggestions about the possible ways to change the compilation or the launching line, write about them in your commentaries.

It should be mentioned that apart from standard verdicts, you can get "Denial of judgement", which usually means that your solution can't be launched, or it has unexpectedly failed. For example, is the Delphi array is too big, the compiler compiles the code, but the result will be the incorrect win32 exe-file. Solutions with the verdicts like "Compilation failed", "Denial of judgement", "Judgement failed" will be ignored while summing the results.

Moreover, pay attention, please, that the problems will be given in English as well as in Russian.

That's it, see you at Codeforces Beta Round#1.

UPD: GCC compiler has been added.

UPD 2: Added Haskell and F#.

UPD 3.2: Actual compiler versions are

  • Mono C# compiler version 3.2.3
  • DMD32 D Compiler v2.064.2
  • Delphi 7 [Borland Delphi Version 15.0]
  • Free Pascal Compiler version 2.6.2
  • MinGW g++.exe (GCC) 4.9.2
  • Haskell Glorious Glasgow, version 7.6.1
  • Java 6 javac 1.6.0_45
  • Java 7 javac 1.7.0_72
  • Java 8 javac 1.8.0_25
  • Ocaml ocamlopt 4.00.1
  • Perl v5.12.2
  • PHP 5.3.8
  • Python 2.7.8
  • Python 3.4.1
  • Ruby 2.0.0p353
  • Scala compiler version 2.11.1
  • MS VS C++ 2010
  • JavaScript V8 3.23.0

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By MikeMirzayanov, 9 years ago, translation, In English,

I will briefly enumerate the changes at Codeforces:

  • Codeforces beta Round #1 is announced. It will go according to the ACM-ICPC rules, but will last for 2 hours. You shouldn't expect much from the problems - in the first place it is organized to check the system function and your feedback. The problems will be in two language: Russian and English. If I finish all the preparatory work earlier, I'll bring the Round some two days forward. It's planned to have the rating system at Codeforces similar to that at TopCoder. If the beta-competition goes without system failures, the participants will get ratings. To take part you are to register first.
  • The visual organization of “Recent actions” has been changed - "new comment" and "compose/edit text" can be seen in the sidebar. Blog entries are sorted by the date of events, it means the last 15 entries are displayed.
  • A new “Recent actions” detailed page, from which you can clearly see who has been doing what in recent time, is introduced.
  • The algorithm of your "contribution" evaluation has been changed. For more details see below. I think I might change something again later.
  • I've fixed some bugs.

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By MikeMirzayanov, 9 years ago, translation, In English,
After a two-day stop in Beijing we're leaving for Moscow. The flight is tomorrow, a bit earlier then 2 p.m. Maybe someone else is flying with us? We land at about 6 p.m., and then we'll have to go to the Paveletsky station, it would be great to catch train 17 that leaves at 19:56. Taking into consideration the number of suitcases we have, it seems that the bus/minibus+underground variant isn't for us. Taxi is the only suitable thing, by the way, does someone know how much it costs to take taxi from the Sheremetyevo 2 Airport to the Paveletsky station?

And if everything goes according to the plan, and we catch the train, we'll arrive at Saratov on February 10 at 12:04. As Antonina Gavrilovna says "tired, but hungry". Wait for us.

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By MikeMirzayanov, 9 years ago, translation, In English,

The results are announced - thanks to Ivan Romanov for being so quick. Thanks to everyone who supported us and followed the contest events. My apologies the system break-down, but if everything was stable in Codeforces, I wouldn't have called it beta. Unfortunately, I had no Internet during the day.


Congratulations to the medalists. The competition was tough.

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By MikeMirzayanov, 9 years ago, translation, In English,
I think I won't find any strength to describe the finishing day. I will only tell you that it was quite tiring - before the trial contest the guys had to wait for about an hour. Then there was a contest almost as long as the real one.

And now about the most important. The official site of the contest is http://icpc.baylor.edu/, and as for the traditional textual broadcast, you'll find it at Snarknews (In Russian)

You start rooting for us on February 5 at 5 o'clock (Moscow time)

Let's express our thoughts and emotions about the contest in the commentaries under this post. I'm not sure, if I'm going to have the Internet during the contest, but if I have such a chance, I'll write something.

UPD: I've nearly forgotten the most important. Today Bill Poucher announced sad news - the finals in Malaysia are postponed, and where they are next year is still kept secret. Rumors say in Cairo (Egypt).

UPD 2: At the informal tournament ICPC Challenge our team advanced to the finals and took the 4th prize. The Final competition is going to take place tomorrow at the closing ceremony.

UPD 3: I think you'll be able to see the results here. Thank you vici, plus for you!

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By MikeMirzayanov, 9 years ago, translation, In English,
Line to open ceremony

The third day was marked by rises and falls of Harbin in our eyes. Everything started with the opening ceremony - it was badly organized, protracted and boring. Right before the opening ceremony the audience went to the assembly hall of the Harbin Engineering University, but the participants were less privileged and had to suffer. We were all gathered in a long basement room, we had to form a line according to predetermined numbers, and wait. As you know, 103 teams take part in the finals, so, about 450 people (coaches and volunteers included) packed into that basement. It was stuffy and crowded there. The Russian teams demonstrated their inherent quick-wittedness, they decided not to stand in the crowd, and moved closer to the entrance, it was cooler and there was more room there.

Finally, to solemn music (be careful, phonogram!) the teams one by one climbed the stage, took pictures and went down to join the audience. As after that according to the program some outdoor activities were planned, many participants had prepared sensibly beforehand, they had put on the presented warm trousers, sweaters, etc. With such a "formal" look they got to the opening ceremony and the shoot. My standing ovation.

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By MikeMirzayanov, 9 years ago, translation, In English,
Перед рейсом

The second day we spent sightseeing - we went to the excursions organized by the host country, some places we visited on our own.

In the morning we had some free time, and we went to the local Arbat (or Kirov Avenue, as you wish). Actually, when we walked not far away from the hotel, we found out that we vaguely knew how to get back. But still we didn't want to go back, that's why we went on moving away, guided by little information we had. It was really cold - but we were well-prepared. I put on a down-filled coat, that we'd got on the first day, over my proper one, foe example. Vova put on the presented trousers over his own jeans, and seemed happy. The parts that got cold were our faces.

On our way to that avenue we asked for the directions many times. The problem was that we didn't remember its name. 80% of passers-by said they didn't speak English, 20% said they did, but it was the only thing they could say in English. Finally, using the international language of gestures, we got the direction and found the avenue. Personally I was disappointed, there was nothing to look at there. Of course, it was interesting to walk past old buildings, but we had no desire to "Russian goods" shops. They sold home-made vodka, chocolate called "Russian fir (pets)" (they meant "pelts"), and other goods of doubtful quality.

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By MikeMirzayanov, 9 years ago, translation, In English,
Set of warm clothes
Everyone got a set of warm clothes. The hats in the photo looked more like scarves at closer inspection. Moreover, we got a set of mustard plasters, which are recommended to be worn under your clothes to keep the body warm.

Three Koothrappali
The Indian team got very excited, when I asked them how popular the TV series The Big Bang Theory is in India.

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By MikeMirzayanov, 9 years ago, translation, In English,
Перед рейсом
The flight went well, without any problems. I always regret that I can't sleep on the plane, and I envy my fellow passengers the ability to sleep their fill during the flight. I managed to fall asleep at the beginning of the first flight only, don't remember how we took off, but didn't miss the meal. After that I didn't sleep at all. The guys seemed to have rested a bit, though, of course, the rest was far from normal. I tried to derive the meaning of some hieroglyphs by comparing the city names in English and in Chinese, but even this didn't help me fall asleep.

We flew 7 hours to Beijing, and 2 more hours from Beijing to Harbin. At Sheremetyevo Airport we met several other Russian teams. The teams from Samara, Izhevsk, and, it seems, Ural were on the same plane. And some other teams. Moreover, we flew with Andrey Styskin, who works for Yandex, and will take part in the conference in the context of the contest. Separate teams could be clearly distinguished on the plane: 3 young people, each with a laptop, or a netbook. However there were exceptions.

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By MikeMirzayanov, 9 years ago, translation, In English,

The team captain Natalia Bondarenko
The team captain Natalia Bondarenko
January 30, 2010 the delegation of the Saratov State University is leaving for the World Finals of the International Collegiate Programming Contest. This year it's held in Harbin (hi, China), and that means that apart from an interesting contest, we have cold weather, ice statues, fried rice with prawns, and as I hope, Beijing Duck.

Our University will take part in the Contest for the 7th time, and for the team Saratov SU#1 this will be the 2nd Finals. It seems to be high time to introduce myself. I'm Mike Mirzayanov, and I'm this team's coach (and also all other teams from my university). In reality I'm the director of Programming Competitions Training Center, but in this case it doesn't matter. I became a part of this so-called olympic movement quite long ago, but since that time I've managed to take part in the finals of the ICPC, and in the finals of Google Code Jam, and onsite competitions by TopCoder (TCO and TCCC both). In brief, I do know what computer programming competitions are, but we won't speak about me.

We will speak about our team Saratov SU#1 and their participation in the coming World Finals. I plan to write a series of articles about our trip to China. No one knows, on whom Lady Luck will smile, and whether we'll return triumphant or defeated, but I hope my account will seem interesting to someone. Any questions? Ask them in your commentaries, and I'll answer them with pleasure.

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By MikeMirzayanov, 9 years ago, translation, In English,
Paveletsky station met us as usual. Taxi, taxi, where are going young man? In the subway suspicious persons sell cellphones near the proclamation: "unauthorized trade is prohibited, fine of 10000 rubles". Fortunately the queue for tickets in the subway has flown by quickly - well, that we got up at first in two, as one moving twice as fast. 

Dima Matov quickly noticed that in Moscow we have arrived too early - beginning tomorrow at Mu-Mu cafes begin discounts of 50%. And when you try to change rubles into something more international we noticed that today is Sunday and banks do not work. Yes, we have arrived in Moscow too early :).

I went to Starbucks and sold Internet for 100 rubles. It was constantly falling off - so I hasten to write these lines before it disconnects again.

In the evening we will sit in the airplane, fly through Beijing, there will be 2.5 hours connection and "Hello, Harbin".

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