Wsl_F's blog

By Wsl_F, history, 2 years ago, In English,
UPD 2 Sep 2018

Hi guys! As I mentioned on previous contest I'm working on tool that predicts rating changes. I'm happy to present it now!

A huge amount of your nerve cells die every time when you wait for a rating update on Codeforces. Stop this! From now you could use this service, it calculates approximate rating changes for every contestant.

The most interested thing for you is extension. It partly modifies the contest standings page and shows approximate rating changes for every contestant. It is available for three browsers:

Extension in work:

Also you could find more detailed information (seed, rank, expected delta, etc.) here.

A project still in beta, so predictions are not very accurate. Average mistake around 5 points, but for the contestants at the back of standings it could be greater up to a few hundreds.

Tech details

I'd like to thank Rubanenko and all other members of NBHEXT developers team for your shared sources and MikeMirzayanov for the great Codeforces platforms with shared API & ratings formulas.

AWESOME UPD

Prediction for todays contest (cf #399) is absolutely matching real rating changes! Thanks for AlexDmitriev! He was close to find my bug in rating calculation:)

UPD

Thanking KieranHorgan now CF-Predictor has a new design. Check it out:)

 
 
 
 
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2 years ago, # |
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Maybe I miss something but why use this, when there is NBHEXT? Did you overcome some of its bugs? Please, give more information on how this differs from NBHEXT :)

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    2 years ago, # ^ |
      Vote: I like it +27 Vote: I do not like it

    NBHEXT not working

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    2 years ago, # ^ |
      Vote: I like it +23 Vote: I do not like it

    NBHEXT predicts rating changes using your browser (did you notice that your browser works slowly and is lagging while doing predictions?) CF-Predictor extension get prediction from own server, so all calculation are made on serverside. And yes, NBHEXT is not working now :(

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2 years ago, # |
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Not for Mozilla? Please make it for Mozilla too.

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    2 years ago, # ^ |
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    It is on validation now. I hope, it doesn't take lot of time:)

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2 years ago, # |
Rev. 3   Vote: I like it -7 Vote: I do not like it

deleted.

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    2 years ago, # ^ |
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    You know, browser extensions work that way that you can enable and disable them whenever you want.

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2 years ago, # |
  Vote: I like it +13 Vote: I do not like it

Funny, on attached screen all but one prediciton were good with tolerance of two points, but tourist's prediciton was way off (by 46 points). Probably there is a bug that comes to light only when we are dealing with very high rated users. Maybe you did same bug as original bug thanks to which tourist once exceeded 4000 points :)?

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    2 years ago, # ^ |
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    Maybe I did not understand bug correctly, but wasn't the rating change caused by tourist beating himself? If it's the same bug, wouldn't the prediction show him as losing more rating, because he lost to himself instead?

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2 years ago, # |
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Please make it for Mozilla too.****

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    2 years ago, # ^ |
      Vote: I like it +8 Vote: I do not like it

    I'm afraid it doesn't happen soon.

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2 years ago, # |
Rev. 3   Vote: I like it +9 Vote: I do not like it

It seems the variance of the tool is quite high. Last contest I got an expected change of +22 (which seemed way off) and the real change was -63. I also saw people with similar results and similar starting rating getting a negative expected rating change.

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    2 years ago, # ^ |
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    This was prediction before system tests. It caused because server gets to many request and have no time to calculate new rating prediction. I will fix this prior next round.

    If you a curious about prediction after system tests you could see it at static page here.

    It predicts to you -65, 2 point lower than actual results.

    sorry for my bugs

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      2 years ago, # ^ |
      Rev. 2   Vote: I like it +5 Vote: I do not like it

      What about showing the last update time of the prediction so that people can know more about it, and also how the prediction should be considered as accurate.

      For instance, from the last update time shown, people can know if the prediction is about middle of the contest, end of contest but before systest, or after systest. So it is much more clear.

      I hope you can consider adding something like this. Thanks for such a great tool anyway:)

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2 years ago, # |
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Auto comment: topic has been updated by Wsl_F (previous revision, new revision, compare).

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2 years ago, # |
  Vote: I like it +1 Vote: I do not like it

Apparently, the rating site is down (at least for me). Any ideas why?

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2 years ago, # |
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The site is up now. But when I try to select a contest and click "Get rating prediction", the results won't display at all. The browser seems to load infinitely instead.

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2 years ago, # |
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I think I found a bug. See this —

He is in my starred user list, He submitted A and got WA on pretest 1 [skipped]. But will this even happen? He will get near +77? o.O

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    2 years ago, # ^ |
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    Yeah, you are right this is bug. mdshs.shanto has a quite low rating (887) and my program calculated his seed as 2922. He took place much higher, so his rating should increase. But official cf rating works somehow different, and I don't know where my mistake((

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      2 years ago, # ^ |
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      Maybe in case of several people on the same place from A to B, you consider their rank to be A, while it's probably considered as (A + B)/ 2;

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        2 years ago, # ^ |
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        I will check this, but in the official shared code rank calculates as in standings:

            private void reassignRanks(List<Contestant> contestants) {
                sortByPointsDesc(contestants);
        
                for (Contestant contestant : contestants) {
                    contestant.rank = 0;
                    contestant.delta = 0;
                }
        
                int first = 0;
                double points = contestants.get(0).points;
                for (int i = 1; i < contestants.size(); i++) {
                    if (contestants.get(i).points < points) {
                        for (int j = first; j < i; j++) {
                            contestants.get(j).rank = i;
                        }
                        first = i;
                        points = contestants.get(i).points;
                    }
                }
        
                {
                    double rank = contestants.size();
                    for (int j = first; j < contestants.size(); j++) {
                        contestants.get(j).rank = rank;
                    }
                }
            }
        
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          2 years ago, # ^ |
          Rev. 2   Vote: I like it +5 Vote: I do not like it

          If all people get same number of points, this code will return contestants.size() as far as I understand the code. In standings everybody would be first

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2 years ago, # |
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Excellent Work! Forked it as Well :)

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2 years ago, # |
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Your tool was perfectly worked yesterday! Thanks man!

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2 years ago, # |
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I suggest to add a Disable/Enable button for the extension as sometimes i wanna to hide it during the contest

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20 months ago, # |
  Vote: I like it +3 Vote: I do not like it

Site is down.I am unable to open it

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20 months ago, # |
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Shows 0 to me ?

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20 months ago, # |
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Now a days, it's not working sometimes. Please pay attention to this. Thanks :-)

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20 months ago, # |
  Vote: I like it +10 Vote: I do not like it

It's still not working!!!

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20 months ago, # |
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CF-Predictor seems to be working now but rating change for #431 Div.2 is wrong. Why?

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    20 months ago, # ^ |
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    The predictor has you placing 289 when your official placing is 338.

    The placing of several top participants appear to be out of order on the predictor.

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19 months ago, # |
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Can sombody help me set this extension up...I added it to chrome extentions...but dont know how it works

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    19 months ago, # ^ |
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    You should just open standings page of active or recently ended contest. You will see a rating change in the last column.

    For example: last contest here

    PS Probably you have a slow internet connection, in this case downloading data could take a while.

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      19 months ago, # ^ |
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      Thats an amazing extension...Almost accurate it showed +20 and I got +21...You did an amazing job

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18 months ago, # |
Rev. 3   Vote: I like it +18 Vote: I do not like it

I think the web interface is really ugly now...

UPD: Great interface now.

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    18 months ago, # ^ |
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    I'm sorry, I'm 100% noob in the frontend. Do you have any better proposal for start page design?

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      18 months ago, # ^ |
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      Just use plain text, no fonts, no styles.

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18 months ago, # |
  Vote: I like it +3 Vote: I do not like it

Auto comment: topic has been updated by Wsl_F (previous revision, new revision, compare).

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16 months ago, # |
  Vote: I like it +5 Vote: I do not like it

Please predict the Good Bye 2017 round's ratings, taking into account the changed ratings due to the last Educational round.

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11 months ago, # |
  Vote: I like it +71 Vote: I do not like it

Please update it to the new rating system.

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    11 months ago, # ^ |
    Rev. 2   Vote: I like it +28 Vote: I do not like it

    I think they have updated it for Div.2 and Div.3 according to the new rating system, but forgot educational rounds :(

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      11 months ago, # ^ |
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      Isn't it the first educational round since new rating was introduced?

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      11 months ago, # ^ |
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      Hi! Could you please tell more specific, what doesn't work?

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        11 months ago, # ^ |
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        In educational rounds rating changes for purple users aren't shown.

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11 months ago, # |
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Wsl_F, it seems that the extension doesn't work for HTTPS version of Codeforces. Please fix.

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    11 months ago, # ^ |
    Rev. 2   Vote: I like it +22 Vote: I do not like it

    Thank you! Updated for Chrome & FireFox! There is some issues with opera. I don't know how soon it be solved.

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      11 months ago, # ^ |
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      Thanks for the fast update, it works now. Tested on Firefox 60.

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      11 months ago, # ^ |
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      Wsl_F, It's still not working on my chrome for HTTPS version :(

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        11 months ago, # ^ |
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        skmonir, could you please check version of extension? It should be 1.2.3

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          11 months ago, # ^ |
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          Wsl_F, yes. It's 1.2.3. In fact, when it wasn't working, I removed it and added again from the chrome web store. So it's latest version.

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    11 months ago, # ^ |
    Rev. 2   Vote: I like it +9 Vote: I do not like it

    You are right. But we can visited this url to find our rating changes.

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10 months ago, # |
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It can't work now.

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    9 months ago, # ^ |
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    Do not worry, everything is fine :) I'll turn it on before the next contest. Free heroku account gives you a limited amount of free hours per month, so I need to spend them wisely :)

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      4 months ago, # ^ |
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      Have you considered Azure Web Services? Don't know if it would work for you, they offer a 1 year free license for students, with a variety of services

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9 months ago, # |
  Vote: I like it +1 Vote: I do not like it

What about Microsoft Edge user???

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8 months ago, # |
  Vote: I like it +3 Vote: I do not like it

Auto comment: topic has been updated by Wsl_F (previous revision, new revision, compare).

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6 months ago, # |
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Why not for safari...???

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4 months ago, # |
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In case the post is too long and it's hard to find links, this is a summary:

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4 months ago, # |
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The predictor was working fine till yesterday. However, today I updated my Firefox web browser and it's not working anymore. I am running Firefox Quantum (64.0) in Ubuntu 18.04.

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    4 months ago, # ^ |
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    no, that's just because the server for cf predictor crashed

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      4 months ago, # ^ |
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      Phew... I thought the newer version is not supported and so I have to reinstall the outdated one.

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3 months ago, # |
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Got Safari and want to stick with it....

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3 months ago, # |
Rev. 2   Vote: I like it 0 Vote: I do not like it

Wsl_F there seems to be some error in rating predictions specially in the latest educational round. Please have a look into this!

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3 months ago, # |
  Vote: I like it +3 Vote: I do not like it

Extensions, get you out of "tension".

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3 months ago, # |
Rev. 3   Vote: I like it +1 Vote: I do not like it

Wsl_F has the CF rating system is being changed.In last contest predictor showed -7 rating change.But it was actually -23

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5 weeks ago, # |
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Wsl_F CF-Predictor hasn't been working for me lately(it doesn't display the delta column)

I'm using Google Chrome and I tried uninstalling and installing it back, but still no success.

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    5 weeks ago, # ^ |
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    I have the same problem with chrome. I have downloaded the Mozila Firefox, where the predictor works.

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      5 weeks ago, # ^ |
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      Same here with Google Chrome is not working.

      Version 73.0.3683.75 (Official Build) (64-bit) for more info

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    5 weeks ago, # ^ |
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    yeah, me too!

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    5 weeks ago, # ^ |
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    I guess we'll have to go back to the tried-and-true method of "Look at your rank and guess the expected delta and then pray you get high rating"

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      5 weeks ago, # ^ |
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      I like your approach! suffering is madatory party of competitive programming :D But if you like, website with predictions still works.

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    5 weeks ago, # ^ |
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    Thank you for reporting, I'll look on this.

    UPD I've found the reason of issue. In last chrome update they changed Cross-Origin Read Blocking policy. And the actual problem is that I can't update code ASAP. I recently started working in Google and they have pretty strict policy about open source projects. I'll try to come up with some solution, but sorry, no promises.

    Current solution is to use website.

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      5 weeks ago, # ^ |
      Rev. 3   Vote: I like it +12 Vote: I do not like it

      Hi Wsl_F, I have fixed the CF-Predictor Chrome extensions and it is working on Chrome 73. I am sending you a PR, please review it and if possible update the Extension as soon as possible.

      UDP1

      YOU SHOULD REALLY WAIT FOR OFFICIAL RELEASE

      For those who want to test it now, Download this, Uninstall the old version as they are signed with different keys. Follow this tutorial on how to manually install chrome extensions. (It's easy).

      UDP2

      To install official extension again, you must remove this

      UDP3

      The new extension is available in the chrome store. Update now

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        5 weeks ago, # ^ |
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        Thank you a lot! Extension has been updated (version 1.2.4) and now it works fine!

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5 weeks ago, # |
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Thanks,it'useful.