Hello, Codeforces! Were you afraid of the lack of contests? We also!
Unfortunately, due to technical problems, the round is declared unrated. You can continue to solve problems, but the results of the current round will not affect your rating. We are sorry for this situation.
Hello! Codeforces Round #697 (Div. 3) will start at Jan/25/2021 18:00 (Moscow time). You will be offered 7 problems with expected difficulties to compose an interesting competition for participants with ratings up to 1600. However, all of you who wish to take part and have a rating 1600 or higher, can register for the round unofficially. The round will be hosted by rules of educational rounds (extended ICPC). Thus, during the round, solutions will be judged on preliminary tests, and after the round it will be a 12-hour phase of open hacks. I tried to make strong tests — just like you will be upset if many solutions fail after the contest is over.
You will be given 7 problems and 2 hours to solve them.
Note that the penalty for the wrong submission in this round (and the following Div. 3 rounds) is 10 minutes.
Remember that only the trusted participants of the third division will be included in the official standings table. As it is written by link, this is a compulsory measure for combating unsporting behavior. To qualify as trusted participants of the third division, you must:
- take part in at least two rated rounds (and solve at least one problem in each of them),
- do not have a point of 1900 or higher in the rating.
Regardless of whether you are a trusted participant of the third division or not, if your rating is less than 1600, then the round will be rated for you.
The problems for this round were invented by MikeMirzayanov and prepared by me Supermagzzz and Stepavly
Thanks to MikeMirzayanov for platforms and coordination of our work. Thanks to darkkcyan, Tzak, bfs.07, songsinger, iankury, spookywooky, Programmer, sodafago, infinitepro for help in round preparation and testing the round.
UPD: Editorial is ready!
7 Problems!!! Great.
Contest start's 15 minutes late
looks like there was some issue with the servers. the site was showing unavailable for me for some seconds.
Codeforces teaching us how recursion looks like
10 more minutes late cant wait to start
A small suggestion, keep an tab open of m1.codeforces.com aside. It might help.
29000 registrations!! they must be adding some resources
Maybe they are waiting for the number of registered participants to cross 30k :0
was fully set to give the contest and the enthusiasm drops down immediately after hearing of delay.Need to think of something to pass time now.Hope to get some upvotes to increase the enthusiasm
please dont do this to me this is my first comment
10 more now
why is this happening?
Making New record of 30k+ coders
again late, but what's wrong ?
contest delayed by 15 minutes update:10 minutes more to go
beacuse they can't check all submissions in time :)
think about your statement for a few minutes...
This is my first contest on codeforces, just got delayed :(
good luch to u
yeah u cant even give them luck dude they are doomed
My first two contests got unrated due to server problem
You are so "lucky" :(
My goodness. See the crowd!! It's highest among all contests that held in cf. Congo cf!
3 mins to go!!! I hope it doesn't get delayed any further :(
lol, it got delayed
Please dont say that again now
Contest start's next 10 minutes late
Can't wait more!!
Is Mike waiting for 30,000 registrations?
100 participants more to cross 30k. :)
As a tester I would like to thank iankury for providing clear explanation.
Some brazilian testers, this is great!
Hope this contest will increase our rating!! Finger crossed.
I will try my best to reach pupil today. All the best to all participants.
I was afraid, but why that happened? contest frequency is decreased this month than other months.
Thanks for the contest.
My chance for pupil!
My chance for expert!
My chance for specialist
my chance to get rated lol
My chance for pupil!
My chance for recover lost rating in last contest.
my chance for experiencing twice delaying of Codeforces
Its 8:25 and I'm still waiting for my chance
How can I become a tester for Div. 3 contests if I am not a friend of the testers/setters?
I am not a friend of either of them. I think it's pure random ;)
Thanks for your reply!
Since I am less likely to give CP contests in the following few months, it would be nice for me to contribute to the CP community by becoming a tester for Div. 3 contests.
I would want to become a Div. 3 contest tester in the future — if Stepavly and Supermagzzz would want me to provide feedback for your contests, please give me a call!
Well, this time each tester has a ten years badge.
I am waiting for a div2 round
I am waiting for a div2 round that is unrated for me :)
7 problems! Wonderful start after an eternal gap.
Are the registrations closed??
No,You can register for the contest.
if i don't get 150+ rating i will do whatever the highest rated reply asks.
What is Obama last name?
is that even a question? Obama's last name is ofc Obama, you idiot
his first name is President
Oh, I thought his last name was gon.
"Care" of course
Solve CF problems at least 3 hours/day for 1 year.
please give me money
We will watch this battle with great interest.
Edit: welp, this would be a disappointing result I guess.
get 150+ rating
ugh, but i guess it doesn't count since my statement is technically incorrect?
What extension or script do you use to highlight submissions based on language?
Would you please provide me the link or more details about is.
google it on chrome's store.
Blog of codeforces enhancer
I am sure nobody likes to see this.
Yes We all know that.
I don't like seeing <"almost-copy-pasted-part>"
That Irregular Bracket Sequence :V
As you can observe now, its_Atrap
As a tester, I recommend participants to open
https://codeforces.com/contest/<contest-id>/problemsrather than opening each problem page, during the contest.
Reduces clutter and server load (ig).
Thanks sir, for this new bit of information.
Can u tell us where we can find the contest-id for contest before the start of the contest Thank you
Enter any contests and you can find the contest-id in the URL.
Edit: You can still find the contest-id in the
/contestRegistrantsroute by clicking and it is
1475for this contest. Luckily, the id gets incremented by one in each contest but you can't enter the contest before it starts.
Actually there are two more or less direct links:
This one links to the contest, but currently forwards to this blog, since the contest has not been started yet:
https://codeforces.com/contest/1475 and is equivalent to the inline link Codeforces Round 697 (Div. 3)
That one links to the page where you can register for the contest:
That second link is also used in Calendar
damn it i just got rick rolled
the real rick roll is in the delays
Thanks to Supermagzzz and Stepavly for preparing the div.3 contest.
After the last contest when it was showing no contest for near future, it was a little bad feeling but now this contest has filled us with new enthusiasm(mind the spellings).
Hoping for less plagiarism in the contest!
Hello everyone its the first div3 of this year and i am here to wish you all good luck for today. Have fun guys.
It is the Second. 1st was #693
Hoping for a great contest.
anyone having difficulties reaching codeforces ?
No, It's working fine for me.
This round has got a crazy number of registrants ~26000, let's hope the round goes smoothly
I already can't visit codeforces.com but I can visit this blog for some reason
I think they postponed the starting time.
Wish the pretest becomes strong.
To all my Indian brothers and sisters Happy Republic Day in Advance. 26th of January is celebrated as Republic Day in India to mark the day when the Constitution of India came into effect. JAI HIND
28k people o_o
I don't even know if that's good or bad lol
3 2 1 .....burrrr!
oh no contest was delayed for 15 mins :(
Dude, 28000+ registrations already, is this the highest up until now ?
Best of Luck Everyone. I wish you all get green in first try:)
thank you i would definitely get green
15 minutes delayed. Drink some water to keep yourself hydrated.
delay is better than unrated.
I hope not both :D
Hope the delay is for good cause. Submissions to be judged fast
garam kar k thanda hi chor diya
waiting for 30k?
For a few seconds, I thought that problems are repeated:)
To All the Indians Happy Republic Day in Advance.
This round is approaching 30,000 participants. This is year's first div 3, right ? Looks like some people are taking their new year's resolution seriously :P
My goodness. See the crowd!! It's highest among all contests that held in cf. Congo cf!
Delayed by 15 minutes. And now I am spending time in the comments section.
Is it the most popular round?
Have Fun & Good Luck!
with that many registrants if i get 3000th position I should be proud
Sorry for the delay.
No, how could you do that to us. :p
HAPPY REPUBLIC DAY TO ALL MY INDIAN BROTHERS AND SISTERS IN ADVANCE
**** **** JAI HIND
and what about non-indians?
You all can celebrate man...we beleive in Vasudhaiva Kutumbakam which means whole word is our family :)
I was waiting this contest. Good luck geeks!
I am excited to see what SecondThread will be doing in these 15+10 minutes in his stream.
The servers seem to be struggling...
Me After Seeing The Delay:-
25 mins late**
Nightmare scenario :D
All the best MikeMirzayanov. 30k incoming!!!!
Highest registered participants.
Congratulations CF on achieving a milestone of 29k participants.
Delayed 10 more minutes ?
Could have had my dinner in 25 mins :( Skipped it for contest
I controlled my shit
Instead of delaying they should close the registration lol.
How come again a delay?
Again it's delayed by 10 mins!!!!!
I think that reason of this delay is good skill for getting more and more participants
Again delayed :(
What is going on??
Why delayed again?
Waiting for 30k ?
It seems it will be delayed until half of the participants go to sleep and we will deal with a normal number of participants.
nice joke, but staff of codeforces is not laughing now
I think they will delay it until 30k people register:)
I think they are waiting for 30k
contest is too much delayed :(
reschedule this contest.
common I am not having dinner just because of the contest and it's getting delayed....
More delay but hopefully rated
it's Monday morning I was just trying to get a quick competition in.. now two delays?
Contest registrations are increasing by O(1) complexity xD
almost 30 thousand registrants ... that's huge!!
30K lmao....hope to become Expert Today
Close to 30k..!! May all registered participants give the contest.
did it just got delayed again? just hope there will be a long queue in the contest. they might be updating pre-test cases due to 29k participants. in order to prevent long queue. (just my guess). good luck to all including (people who made this round.)
What is wrong? Contest has been reschedule twice already :|
Can you reschedule the round again?
Don't extend it again
Are you kidding me?
That contest is put off 10min again means I couldn't get at least 4h to sleep in CHN.
Div-3 be like.. wait 10min more..;)
Why the contest is delayed?
Atleast tell us the reason for the delay.
I think it's due to the huge number of participants. what do you think?
everyone is waiting
Now we have record of participants, but I think for another delay we will have antirecord
Now codechef might just get a new excuse XD
Its 30 minutes late. Why ?
I have to eat food..
ну иди поешь)
Cheers to everyone who has participated in the contest with maximum registered participants!
Why is the contest getting delayed??????????? I entered at 8:05pm IST to find out that the contest is starting at 8:20pm IST. When I enter at 8:20pm IST, it is showing delay of further 10 minutes!!
may be some question is wrong
Maybe they're testing if the servers can handle the load
but that is not good idea, delaying also increases number of registrants..
new year resolution effect 30k
There should be an option for unregistration from contest if delays come.
30k participants, This contest is going to be very much fun.
until I see -150 delta.
please no more delay :(
codeforces randi ,start krrde
You want me to find you on LinkedIn and send this comment to your recruiter? Delete it fast little bitch.
We often get stressed during or even before the contests, which leads to frustration. Keeping that in mind and not to forget the constant delays today i would like to appologise to absolutely nobody, do what u can , the king does what he wants.
Your frustration results in you calling this platform a "whore"? And you're no king. Just a sad pussy behind a keyboard. Don't shit where you eat. If you can't respect the platform then leave. Everybody here is "frustrated" but nobody is using these stupid insults like you.
I will not respect the platform and I'll not leave either. What can u do about it Mr. Authority?
I hope this countdown is not a countdown to the next delay
Come on!!!! My mom will beat me if i will not eat my dinner at time.
I'm rooting for your mom.
My mom even don't listen to my father.
They're gonna keep delaying the contest until some people unregister because of frustration :D. Don't blame them though, this is a historical milestone.
YES!! yEEEE! 30.000!gogogoGO! yEEEEEEEEEEES!!!!
Me watching contest getting delayed , after waiting for 1 month for div3 -
was the delay to hit 30k registrants lol
Now I am 16 years old.
When Contest starts, I will be 116 years old :D.
Highest number of participants in Codeforces history.
If it takes so much time to reload use m1.codeforces.com , m2.codeforces.com or m3.codeforces.com.
Contest will be delayed for 10 mins. If it doesn't start in 10 minutes just read first sentence again.
Congratulations for having 30K coders today.
Don't delay it anymore.OK?
Mike just wants achieve 30k :D
Number of comments increased by 200% due to this delay.
as well as no of downvotes for this blog :(
the delay might be to get 30,000 no of participants
30k on codeforces round!!! Congratulations!!
RECORD! It's 30k.
Seems like, cp has become like engineering in India, you have to do it, whether you like it or not.
look at 30K participants
Thanks to indian youtubers for making this possible -_-
Congratulations for 30k participants! This has been such a great platform.
There we go 30000+ registrations !!
25 mins late but... a new record :')
Congrats CF for 30k participants..
Congratulations CF on achieving a new milestone of 30k participants.
20:04: Me to Mom: Mom, I will have dinner at 10:05.
20:05: Me to Mom: Let have dinner now; I will eat fast.
20:20: Me to Myself: Well wtf I ate so fast? Let write a comment and let the entire community know :)
20:30: Me to Myself: All the best :)
21:00: Me: Please Codeforces, make it unrated, unable to bear queue timings :)
21:15: Regardless of rated/unrated, I stop giving the contest. #queueforces
21:20: I enjoyed the problems, will upsolve them later when the queue is not long, also Congrats on the 30k+ registration.
oh no! Queue of 5 min.
How do you know the length of the queue?
I've been waiting for 10 mintues and it's still not judged. So that's how I know.
TOOO LONG QUEUE uNRATED PLZ
o shit queue that too for this long
in queue "unrated"
please make this round unrated....very long queue timing..!!
Yes, please make it unrated. The queue is of more than 20 minutes.
Am I a noob king or C is actually tough.... Lol
Shut Up! You are not allowed to discuss about problems during contest.
make this contest unrated!
From this page onwards for quite a few pages of submissions. (the page number will change as time goes, so a little ahead or behind, around 30 pages from the last page)
Shady activities. [Edited/]
Someone is purposely overloading the server. There are many accounts that have been created around 11 days back which have submitted codes that have lead to compilation error.
Why tho? :/
They may be college freshers
Probably not, the names are spammy, all created on the same day, submitted and went offline around the same time, submitted compilation errors around the same time. Very hard for it to be freshers, the names and profiles don't look genuine.
Make it an unrated contest please.. queues are unbearable
At this point they should just make this unrated, the queue is unbearable
Codeforces is really a awesome platform
In div-3 no of solution submit frequency is so much.
So, If in div-3, only <1600 rating people can attend thats much better for the server i think. >=1600 rating can practice it virtually though (:
Most of the participants in CF are below expert or unrated so that wouldn't matter
and i did not said by that all problem solved but can reduce (: just my opinion sir.
but that's 5k people submit 5k*7 solution in first hour mostly. cause they solved all before 1 hours. and initial time is most important.
The fact that the contest isn't rated for someone doesn't means that it cant be enjoyable on a competitive point of view
Contest has been declared unrated!!!!
I think everyone got the notification...
Why codeforces why?
Well not just a registrants record also a queue record
2021 == Extended Version of 2020 .
2021 == 2020 won and now it wants have some fun :)
30 000 participants dissapointed for the first time
So we were trying not to annoy delays for this?!!
to cc and cf : you either die a hero or live to become the villain
When CF Predictor shows +200 and the round becomes unrated...Sed lyf
Please consider restricting new acccounts from participating div.3 (more than $$$5500$$$ out of $$$30000$$$, two times as the number of $$$1600+$$$ people. It's really weird.) or upgrade the judge system. The number of participant is too high for the current system (or the system is a bit off today?)
Maybe I should call it Qulayforces,right?
I guess, CF should only allow participants whose rating less than 1600 even to enter the problem-set page for Div 3.
This will increase the no. of people having rating greater than 1600 to participate with a new round , which will have a big adverse effect.
I do understand your concern, but I guess Div3 are meant to be beginner friendly (Please correct me if I am wrong), and in such a case, why could it be only allowed to participants below 1600. (Also, If I had offended anyone, apology). I wouldn't say that high rated people shouldn't take part in lower Division contests. But given the possible scenarios of long queues and site getting down, It could be a suggestive measure.
Suggestion is good but I think it is not practical
Is Codeforces taking inspiration from codechef nowadays?
Never in it's lifetime will Codechef have such a huge number of participants.
Queue 260 pages long :(
I'd love to sacrifice my Internet/CPU/Screen space to see ads on this website just to have better servers. Please admin consider this way of getting better servers.
I had such a bad spree and now cf predictor showed +115 and round is unrated... brb gonna drink some bleach with vodka
Very disappointing! Considering that there were 2 delays and the round was delayed by 25 minutes, it seems that they understood what was happening. Perhaps it was worth postponing the round a few days in advance, having solved the technical problems before. This is doubly sad because the tasks were interesting :(
They tried to prevent such unexpected issues by delaying the round a bit but still it could not be prevented :(
Anyways beautiful problem set! :D
The sad part is that today my exams got over, and I was like finally I can give the contest without much thinking about studying for exams.
Is that a coronavirus on your profile?
lol no! Its a polygon with thousand sides! That is a chiliagon!
Getting a +150 increase and seeing contest becoming unrated hurts :(
What is the procedure in this case? Can people discuss problems already as ratings are not impacted?
i think you can discuss with friends but not in the comment section
Sorry guys. I could not prevent the round from failing, as I was at the doctor's appointment.
Still infinite times better than Yesterdays Codechef cook-off.
But that was rated.
beside unbalanced div2 & div1,they said they have improved servers before contest , then servers didn't worked during the contest for 30 minutes , created unfair ranking gaps and then they were stubborn enough to make it rated .
Codechef is a joke nowadays. Only 2 short contests per month and that too getting server errors a lot, you can't even open IDE to submit the code forget about long judging time, similar thing happened in december as well. No wonder why CF is 10 times better than CC.
No problem MikeMirzayanov. Altough Iam sad about this round but ..... Get well Soon.
Got it. A ship was wrecked when the captain went to the doctor's.
First time I solved 3 problems in a contest. But unfortunately It is now UNRATED...sad
I was getting around 100+ rating in this contest but luck cannot favour you always :(
Remember! there's also people who left the contest earlier.
Problem G is not available on m2.codeforces.com, which is more strange than queue problem.
Remove div3 from codeforces. It was pointless idea from the beginning and as for now servers are not able to handle 30k submissions for easy problems and I don't think they will able in the near future. You're only disappointing people.
I think this is not solution
It is solution. Have you ever seen a queue on div1 round? Div2 rounds were unrated due to queue, as I know, but queue was caused by server issues (and extremely easy problem A and B). Today servers were on full power but anyway they weren't able to judge easy problems without queue. Removing div3 and making div2 harder will definitely solve queue issues.
Of course we can solve problem with this for temporarily but when codeforces get bigger few years later this solution is useless
I could bet if you were pupil, you wouldn't make this comment
What's the point of div3 round for you (and pupils)? Practice? No, you will never reach even expert if your practice consists only of div3 ABC problems. Compete? No, your CP level is too low for real competition. Competing with this level and being happy with 2000th place on contest instead of 3000th, instead of practicing, won't raise your rating and you'll be pupil for life.
Please make it rated, I'm getting 140+ delta :) :(
Cool, you got 140+ delta after most people left ;)
Ohh that's the reason for this miracle. I thought I done some extraordinary work today :)
-- Problem A, Odd Divisor
This problem asks us to check all divisors of n if there is an odd one among them. Note that the constrainst are set in a way the the simplest implementation of the factorization will go TLE. see https://cp-algorithms.com/algebra/factorization.html
Edit: Or just check if there is an divisor other than 2.
-- Problem B, New Years Number
Note that n is fairly small. So we can check all multiples of 2020, and if the difference to n is divisable by 2021. If none of them is, then ans is NO, else YES.
-- Problem C, Ball in Berland
We need to choose two pairs. So, we need to know foreach pair p1 the number of other pairs we can choose, if we have choosen p1. That number is the number of all pairs, minus the number of pairs having the one or the other member of p1 as a member.
Since each pair is distinct, we can count the frequency of all members in all pairs, and subtract that frequency from the number of all pairs.
-- Problem D, Cleaning the phone
Its a strange greedy. We can sort the applications by storage units per cost unit. So simply double the storage units of the 1-cost apps, then sort them. Then we choose the best ones until enough storage is cleaned. If not possible then ans=-1.
But, it can be that we can substitute one 2-cost app by a 1-cost app. For that, check if there is a not choosen 1-cost app that we can exchange agains the worst choosen 2-cost app, so that still enough storage is cleaned.
Not sure how to prove that there cannot be more than one such substitution.
-- Problem E, Advertising Agency
Of course we must choose the best bloggers first. But there can be equal bloggers, and if there are equal ones, we can choose among them.
Consider the number of followers of the worst of the choosen bloggers. Let cA be the number of bloggers with the same number of followers as that worst one. And cC be the number of bloggers with same followers as worst, and wich are choosen. Answer equals nCr(cA, cC). This is, because we can choose any cC of those bloggers among the cA ones.
-- Problem F, Unusual Matrix
Observe that it does not make sense to flip a row or col twice. Flip it once or not at all.
Then consider the first row. We can flip it or not-flip it. In both cases, we can see foreach column if it was flipped or not by comparing the fields of the first row of a and b. As a result we get the state of each col, flipped or not-flipped.
Then check all other rows if we can construct the b version of the row by using the column flips on the a version. If this is possible for all rows then answer is YES, else NO.
-- Problem G, Strange Beauty
We find the biggest possible set of numbers we can put into an array, then the difference to the number of all elements is ans.
Consider that we have put one number into the array. The next one must be a multiple of the first one. And then the next must be a multiple of the LCM of the first two ones... It turns out that because the last added number is allways a multiple of all numbers previously added, we can allways add each multiple of the previous number. So we can create a graph where each number has an edge to each multiple of it, then find the longest path in that graph.
Other possibility is a dp, where dp[i] is number of elements that can be added after having added element i.
Problems were really cool, thanks!
A could be solved by checking if N is a power of 2 and outputing false if it is, else true
B can also be solved by removing as many 2020s as possible, ur left with only 1s to add to the 2020s removed, if there are more 1s than 2020s removed, then its false, else true
Wow, cool, I did not see this.
Another approach for D:
Fix the number of 1 cost applications and binary search to find how many 2 cost you need to take
Every time I will forget that we can construct an algorithm with time complexity O(n + n/2 + n/3 + .......n/n).
I have tried D with the same approach but it is not working can you tell me my mistake here is the link to my submission https://codeforces.com/contest/1475/submission/105410745 This approach is similar to spookywooky
Not sure about that. Mine looks like this 105418791
Video Tutorial A and B:https://www.youtube.com/watch?v=vMpkqoZZN0I
I don't see a single submission from your handle, why should one trust your solutions?
I was wondering how that person was able to solve an problem C and problem E and problem G in one minute???
problem A in minute 4
problem B in minute 5
problems C & E & G in minute 6???
His submissions are skipped