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I hope it will be a good contest!

I hope this round will rebuild our shattered hope on easy rounds.

Vovuh's rounds are always good!

After this contest my final exam will be started....But I will keep doing contest

Best ways to increase your contribution :)

Thanks MikeMirzayanov for adding Diagnostics Hint feature on RE.

I hope it'll be a good contest;

This is participants attending this contest at night 24:00.

Will the downtime of polygon affect us? Will there be testing in the contest?

I didn't do much with my youtube channel recently because I was busy with summer schools and stuff, and this is bad for publicity :)
So I guess I will do screencast with English commentary for this round and I'll try to go more in depth about solutions. That is, if Mike and team will fix Polygon. Hope to see you on the channel!

Is there any negative point for the unsuccessful hacking attempt during the 12 hours of hacking period?

Unfortunately there is an issue with CF-Predictor and it will not be available during coding phase of this contest. CF-Predictor is going to be back after 22:00 UTC today.

I'm very sorry for the inconvenience.

Me before Contest : second thing don't tell what you think I will be I'm the one at the sail I'm the master of my seeeeooh oooh
After Contest : Paaaaaain you made a you made a believer

No stress Happy round

Long queue times anyone?

Long queue times anyone? Sorry posted previous comment in russian :C

Oh my god! Queueueueueueforces

The system is not allowing me to submit even a single solution. It is always showing "You have submitted exactly the same code before". please help!!

Thanks for the round. It sucks. Can u fix your servers pls, the submission was in queue for about 7 minutes. Make it unrated or increase the time. Thanks

contest should be unrated i submited my solution 12 mins ago

Queueforces Div3

I use gmail for codeforces. How can i enter in codeforces2?

MY CUR PING : 600000 ms and it keeps on increasing :/

MY CUR PING : 600000 ms and it keeps on increasing :/

pls make it unrated!!!

Contest extended by 20 minutes, but the situation that has already happened cannot be reversed. It's not good for successful contest. :(

make this round unrated

Wondering what happens if you hack a solution, and it gets compilation error.

Me waiting for the verdicts.

deleted

Is there a solution in python that runs in time for D2? If not, then why support it at all! frustrated ^^ The problem was very nice to think about, thank you — I am curious what I did wrong...

What is TC 37 in F1 ?

Sorry for slow website and judge queue. I think it was the first major queue during the last months. Actually, I do not understand the reason for now: is it because of too heavy tests + easy problems or there is another reason. I'll investigate it. I'm doubly upset because I was thinking about ideas for these problems for several days (it seems that all ideas belong to me). I hope you enjoyed the problems!

Upd: now I got what is the problem with C. Can you tell me what is wrong with other ones?

Can someone please tell me why I got WA on all of my submissions in this contest? (except A)

https://mirror.codeforces.com/contest/1203/submission/58755675

https://mirror.codeforces.com/contest/1203/submission/58763681

https://mirror.codeforces.com/contest/1203/submission/58744361

https://mirror.codeforces.com/contest/1203/submission/58770060

What is testcase 33 in D2?

Failed to solve a QUEUE question in interview this morning, and now CF is showing me QUEUEEEEEEEEE. God's pun game is strong :(

Could have made WA to AC if it wasn't QUEUEEEE, this is frustrating..

I think the order should have been C-A-E-B-D-F, but I suppose it doesn't really matter in Div 3 contests.

how to solve F2? I spent 2 hours thinking :( . Is there some standard algorithm?

in queue:)

R.I.P QUEUEFORCES

36 hours hacking phase?

F2 is similar to Problem I in NWERC2017.

why is the open hacking phase of 36 hrs??

this contest — queue = PERFECT!!

Why the duration of open hack is 36 hours, not 12?

Why does the timer for open hacking (https://mirror.codeforces.com/contest/1203/standings) say that the open hacking phase lasts over 35 hours?

still 36 hours open hacking?

Contest was nice.

This contest should get unrated. I had to wait for a long time to see the whether the test cases passed or not. This wasted a lot of time of mine.

it seems Dsiv.3 always have a huge number of participations this round have a 13216 participations, which I think is one of the most participations in contests. maybe it should increase the number of Div.3?

Screencast with commentary

How to use m2.codeforce?

I only use the auto?(one click?) login of Gmail.

Please help with the solution of F2

I'm getting WA on test case 18 in problem D2. Could someone help me to figure out what is going wrong. This is my submission 58778018. Thanks in advance.

how to solve f1 ??

Does the hacking in hacking phase gives points?

How to sort the input in optimal order in F2 ?

In question C I got TLE in this submission 58730683 and pretest passed in this 58757237 can anyone explain why ??????

I think the problems are really great, if it not were for the technical issues it might be an excellent contest.

Best ways to get downvotes in a div.3 post:

Lv.1 wish a good contest!

Lv.2 No broken div.3 again!

Lv.5 WTF, this is a div.2 or even div 1.5!

Lv.10 See this is good examples of div 3...........

Lv.100 This comment is hidden because of too negative feedback, click here to view it

Lv.999 Please give me upvotes.

The common divisor of 2 integers $$$a, b$$$ is the divisor of $$$gcd(a,b)$$$. I tried to prove in the way.
Every integer $$$x$$$ can be rewrite under the form of multiple of prime factors:

$. &

We construct $$$gcd(a, b)$$$ by choosing all common prime factors p with the lowest exponent each factor.

And, we construct a arbitrary common divisor by choosing some common prime factors with the exponent each factor always less or equal to the lowest (i choosed in gcd).
Following this manner, the common divisor of $$$a, b$$$ is always divisor of $$$gcd(a, b)$$$.

I think this Codeforces round is a bit easy, but it's still very good, too. A good writer with a good round.

thank to the extend 20 minutes, I can solve the D2 in the last minute. however, waiting for 3 problems' judge is not a good feeling. hope nobody hack me so that i can be an expert this time.

How to solve D2 Remove the Substring (hard version)(https://mirror.codeforces.com/contest/1203/problem/D2) ?

is this contest rated??

Can F1/F2 be solved by some Greedy approach? Many solved it by Dynamic Programming. I tried Greedy during the contest but it failed.

Добрый день!

я получил сообщение, о том, что мой код на С задачу идентичен решению другого пользователя. Я хотел бы сказать, что это не случайность. Я действительно скопировал его код, о чём сейчас сожалею. Прошу прощения за нарушение правил и обещаю, что такого больше не повториться

Спасибо

Can someone explain the idea behind problem D?

I have got this message from System

Attention!

Your solution 58745781 for the problem 1203D1 significantly coincides with solutions Sukarna_Paul/58745781, ManBug/58766521, CODE_IS_LIFE/58770117. Such a coincidence is a clear rules violation. Note that unintentional leakage is also a violation. For example, do not use ideone.com with the default settings (public access to your code). If you have conclusive evidence that a coincidence has occurred due to the use of a common source published before the competition, write a comment to post about the round with all the details. More information can be found at http://mirror.codeforces.com/blog/entry/8790. Such violation of the rules may be the reason for blocking your account or other penalties. In case of repeated violations, your account may be blocked.

But I don't even know those guys with whom my code has been matched . Even I myself surprised how it matched . Its a coincidence for sure .

Problem F is a cleverly disguised "regular bracket sequence" problem. See 1745 on timus.

Editorial by me incase anyone still needs it:

A. Circle of Students

def solve(N, A):
    i = A.index(1)
    A = A[i:] + A[:i]
    return (all(A[i] == i+1 for i in xrange(1, len(A))) or
            all(A[i] == N+1-i for i in xrange(1, len(A))))

B. Equal Rectangles

from collections import deque
def solve(A):
    D = deque(sorted(A))
    area = None
    while D:
        lo1, lo2 = D.popleft(), D.popleft()
        hi1, hi2 = D.pop(), D.pop()
        if lo1 != lo2 or hi1 != hi2:
            return False
        elif area is None:
            area = lo1 * hi1
        elif area != lo1 * hi1:
            return False
    return True

C. Common Divisors

from fractions import gcd
def solve(A):
    g = reduce(gcd, A)
    ans = 1
    d = 2
    while d * d <= g:
        e = 0
        while g % d == 0:
            g /= d
            e += 1
        ans *= e + 1
        d += 1 + d & 1
    ans *= 1 + (g > 1)
    return ans

D. Remove the Substring

def solve(S, T):
    j = 0
    ixs = [-1]
    for i in xrange(len(S)):
        if j < len(T) and S[i] == T[j]:
            ixs.append(i)
            j += 1
    
    j = len(T) - 1
    jxs = [len(S)]    
    for i in xrange(len(S) - 1, -1, -1):
        if j >= 0 and S[i] == T[j]:
            jxs.append(i)
            j -= 1
    
    # ixs[t], jxs[t] = "i" and "j" for split of T[:t] and T[t:]
    return max(j-i-1 for i, j in zip(ixs, jxs[::-1]))

E. Boxers

from collections import Counter
def solve(N, A):
    count = Counter(A)
    ans = 0
    for demand in xrange(1, 150002):
        for d in (demand-1, demand, demand+1):
            if count[d] > 0:
                count[d] -= 1
                ans += 1
                break
    return ans

F. Complete the Projects

def solve(N, R, projects):
    pos, neg = [], []
    for proj in projects:
        if proj[1] >= 0:
            pos.append(proj)
        else:
            neg.append(proj)

    ans = 0
    pos.sort()
    for a, b in pos:
        if R >= a:
            R += b
            ans += 1

    neg.sort(key = sum, reverse = True)
    dp = [[0] * (R+1) for _ in range(len(neg) + 1)]
    # dp[i][r] : how many projects from neg[i:] with rating r
    
    for i in range(len(neg) - 1, -1, -1):
        for r in range(R, -1, -1):
            a, b = neg[i]
            dp[i][r] = dp[i+1][r]
            if r >= a and r + b >= 0:
                dp[i][r] = max(dp[i][r], dp[i+1][r+b] + 1)
    return ans + dp[0][R]

Can anyone please help me to understand the problem E? I dont understand the problem for a while. It would be really helpfull. Thanks in advance. :)