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### mesanu's blog

By mesanu, history, 2 months ago,

Thank you for participating!

1971A - My First Sorting Problem

Idea: flamestorm

Tutorial
Solution

1971B - Different String

Idea: flamestorm

Tutorial
Solution

1971C - Clock and Strings

Idea: flamestorm

Tutorial
Solution

1971D - Binary Cut

Idea: flamestorm

Tutorial
Solution

1971E - Find the Car

Idea: mesanu

Tutorial
Solution

1971F - Circle Perimeter

Idea: mesanu

Tutorial
Solution

1971G - XOUR

Idea: mesanu

Tutorial
Solution

1971H - ±1

Idea: flamestorm

Tutorial
Solution
• +64

By mesanu, history, 5 months ago,

Thank you for participating!

1926A - Vlad and the Best of Five

Idea: flamestorm

Tutorial
Solution

1926B - Vlad and Shapes

Idea: mesanu

Tutorial
Solution

1926C - Vlad and a Sum of Sum of Digits

Idea: flamestorm

Tutorial
Solution

1926D - Vlad and Division

Idea: mesanu

Tutorial
Solution

1926E - Vlad and an Odd Ordering

Idea: flamestorm

Tutorial
Solution

1926F - Vlad and Avoiding X

Idea: flamestorm

Tutorial
Solution

1926G - Vlad and Trouble at MIT

Idea: mesanu

Tutorial

Solution coded by Dominater069, thanks!

Solution
• +69

By mesanu, history, 10 months ago,

Thank you for participating!

1873A - Short Sort

Idea: flamestorm

Tutorial
Solution

1873B - Good Kid

Idea: mesanu

Tutorial
Solution

1873C - Target Practice

Idea: flamestorm

Tutorial
Solution

1873D - 1D Eraser

Idea: flamestorm

Tutorial
Solution

1873E - Building an Aquarium

Idea: flamestorm

Tutorial
Solution

1873F - Money Trees

Idea: mesanu

Tutorial
Solution

1873G - ABBC or BACB

Idea: flamestorm

Tutorial
Solution

1873H - Mad City

Idea: mesanu

Tutorial
Solution
• +72

By mesanu, history, 10 months ago,

Hello Codeforces!

flamestorm, MikeMirzayanov and I want to invite you to Codeforces Round 898 (Div. 4).

It starts on Sep/21/2023 17:35 (Moscow time).

The format of the event will be identical to Div. 3 rounds:

• ICPC rules with a penalty of 10 minutes for an incorrect submission;
• 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
• after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
• by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).

We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the official participants.

Only trusted participants of the fourth division will be included in the official standings table. This is a forced measure for combating unsporting behaviour. To qualify as a trusted participant of the fourth division, you must:

• take part in at least five rated rounds (and solve at least one problem in each of them),
• do not have a point of 1400 or higher in the rating.

Regardless of whether you are a trusted participant of the fourth division or not, if your rating is less than 1400 (or you are a newcomer/unrated), then the round will be rated for you.

Many thanks to the testers: Gheal, Phantom_Performer, KrowSavcik, haochenkang, sandry24, BucketPotato, Vladosiya, NintsiChkhaidze, erekle, Dominater069, MADE_IN_HEAVEN, Qualified.

We suggest reading all of the problems and hope you will find them interesting!

Good Luck!

• +200

By mesanu, history, 12 months ago,

Thank you for participating!

1850A - To My Critics

Idea: mesanu

Tutorial
Solution

1850B - Ten Words of Wisdom

Idea: flamestorm

Tutorial
Solution

1850C - Word on the Paper

Idea: flamestorm

Tutorial
Solution

1850D - Balanced Round

Idea: SlavicG

Tutorial
Solution

1850E - Cardboard for Pictures

Idea: flamestorm

Tutorial
Solution

1850F - We Were Both Children

Idea: mesanu & SlavicG

Tutorial
Solution

1850G - The Morning Star

Idea: flamestorm

Tutorial
Solution

1850H - The Third Letter

Idea: SlavicG

Tutorial
Solution
• +78

By mesanu, history, 16 months ago,

Thank you for participating!

1807A - Плюс или минус

Idea: flamestorm

Tutorial
Solution

1807B - Хватайте конфеты

Idea: mesanu

Tutorial
Solution

1807C - Найти и заменить

Idea: flamestorm

Tutorial
Solution

1807D - Нечётные запросы

Idea: SlavicG

Tutorial
Solution

1807E - Интервью

Idea: SlavicG

Tutorial
Solution

1807F - Мяч-попрыгунчик

Idea: mesanu

Tutorial
Solution

1807G1 - Последовательное сложение (простая версия)

Idea: flamestorm

Tutorial
Solution

1807G2 - Последовательное сложение (сложная версия)

Idea: flamestorm

Tutorial
Solution
• +20

By mesanu, history, 18 months ago,

Hello Codeforces!

flamestorm, SlavicG, MikeMirzayanov and I want to invite you to Codeforces Round 849 (Div. 4).

It starts on 03.02.2023 17:35 (Московское время).

The format of the event will be identical to Div. 3 rounds:

• ICPC rules with a penalty of 10 minutes for an incorrect submission;
• 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
• after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
• by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).

We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the official participants.

Only trusted participants of the fourth division will be included in the official standings table. This is a forced measure for combating unsporting behaviour. To qualify as a trusted participant of the fourth division, you must:

• take part in at least five rated rounds (and solve at least one problem in each of them),
• do not have a point of 1400 or higher in the rating.

Regardless of whether you are a trusted participant of the fourth division or not, if your rating is less than 1400 (or you are a newcomer/unrated), then the round will be rated for you.

Many thanks to the testers: _Vanilla_, badlad, Gheal, Phantom_Performer, Beacon, Nihad_Nabelsi, prvocislo, keta_tsimakuridze, Bakry, RedstoneGamer22, tibinyte, KrowSavcik, haochenkang, myvaluska, sandry24, BucketPotato, Vladosiya, pashka.

We suggest reading all of the problems and hope you will find them interesting!

Good Luck!

UPD: Editorial is posted.

• +261

By mesanu, 23 months ago,

Hello Codeforces!

flamestorm, MikeMirzayanov and I want to invite you to Codeforces Round 817 (Div. 4).

It starts on 30.08.2022 17:50 (Московское время).

The format of the event will be identical to Div. 3 rounds:

• ICPC rules with a penalty of 10 minutes for an incorrect submission;
• 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
• after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
• by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).

We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the official participants.

Only trusted participants of the fourth division will be included in the official standings table. This is a forced measure for combating unsporting behaviour. To qualify as a trusted participant of the fourth division, you must:

• take part in at least five rated rounds (and solve at least one problem in each of them),
• do not have a point of 1400 or higher in the rating.

Regardless of whether you are a trusted participant of the fourth division or not, if your rating is less than 1400 (or you are a newcomer/unrated), then the round will be rated for you.

Many thanks to the testers: sandry24, SlavicG, tibinyte, Gheal, qwexd, haochenkang, TimDee.

We suggest reading all of the problems and hope you will find them interesting!

Good Luck!

UPD 1: The contest is delayed by 15 minutes.

UPD 2: The opinions of testers about the order of problems are very contradictory. Please do not rely heavily on the order of problems in the round and read all the problems. Good luck!

UPD 3: Editorial is out!

• +172

By mesanu, history, 2 years ago,

Hello Codeforces!

SlavicG, flamestorm, MikeMirzayanov and I want to invite you to Codeforces Round 806 (Div. 4).

It starts on Jul/12/2022 17:35 (Moscow time).

The format of the event will be identical to Div. 3 rounds:

• ICPC rules with a penalty of 10 minutes for an incorrect submission;
• 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
• after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
• by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).

We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the official participants.

Only trusted participants of the fourth division will be included in the official standings table. This is a forced measure for combating unsporting behavior. To qualify as a trusted participant of the fourth division, you must:

• take part in at least five rated rounds (and solve at least one problem in each of them),
• do not have a point of 1400 or higher in the rating.

Regardless of whether you are a trusted participant of the fourth division or not, if your rating is less than 1400 (or you are a newcomer/unrated), then the round will be rated for you.

Many thanks to the testers: TimDee, Gheal, Max_Calincu, qwexd, _Vanilla_,sandry24, jampm, haochenkang, tibinyte, Etherite.

We suggest reading all of the problems and hope you will find them interesting!

Good Luck!

Update: Editorial

• +151

By mesanu, 2 years ago,

Hello Codeforces!

SlavicG, flamestorm, MikeMirzayanov, Errichto, and I want to invite you to the long-awaited second Div. 4 round!

It starts on Apr/21/2022 17:35 (Moscow time).

The format of the event will be identical to Div. 3 rounds:

• ICPC rules with a penalty of 10 minutes for an incorrect submission;
• 12-hour phase of open hacks after the end of the round (hacks do not give additional points)
• after the end of the open hacking phase, all solutions will be tested on the updated set of tests, and the ratings recalculated
• by default, only "trusted" participants are shown in the results table (but the rating will be recalculated for all with initial ratings less than 1400 or you are an unrated participant/newcomer).

We urge participants whose rating is 1400+ not to register new accounts for the purpose of narcissism but to take part unofficially. Please do not spoil the contest for the official participants.

Only trusted participants of the fourth division will be included in the official standings table. This is a forced measure for combating unsporting behavior. To qualify as a trusted participant of the fourth division, you must:

• take part in at least five rated rounds (and solve at least one problem in each of them),
• do not have a point of 1400 or higher in the rating.

Regardless of whether you are a trusted participant of the fourth division or not, if your rating is less than 1400 (or you are a newcomer/unrated), then the round will be rated for you.

Many thanks to the testers: senjougaharin, magnus.hegdahl, Vladosiya, MeGustaElArroz23, Sho, bakekaga, geranazavr555, doreshnikov, jampm, Neophiliatic, qwexd and VIP-tester _Vanilla_.

We suggest reading all of the problems and hope you will find them interesting!

Good Luck!

Update: Editorial

• +432

By mesanu, history, 3 years ago,

1537A - Arithmetic Array

Tutorial
Code

1537B - Bad Boy

Tutorial
Code

1537C - Challenging Cliffs

Tutorial
Code

1537D - Deleting Divisors

Tutorial
Code

1537E1 - Erase and Extend (Easy Version)

Tutorial
Code

1537E2 - Erase and Extend (Hard Version)

Tutorial

Solution by Ari.

Code

1537F - Figure Fixing

Tutorial
Code
• +154

By mesanu, history, 4 years ago,

## Hello Codeforces!

SlavicG and I are glad to invite you to Unofficial Div 4 Round #2. Which will take place this Wednesday at 14:35 UTC (The round is over now, but you can still participate virtually). The round will not be rated for any participants since it is unofficial.

You will be given six tasks and two hours to solve them. The problems were created and prepared by mesanu and SlavicG for users with a rating range from 0 to 1400 but anyone is welcome to participate in the round!

We want to thank everyone who was involved in the round preparation:

Errichto for thorough testing and publishing this round on the gym.

Also, after the contest Errichto will post videos about this contest and the responsibilities of a tester.

UPD: Videos are now up: Fixing A, Testing A, Testing the rest.

Brodicico for help with problems and testing the round.

And a huge thank you to the testers: Errichto, Monogon, galen_colin, gupta_samarth, arujbansal, Chihai_Ion and Grumpah .

MikeMirzayanov for Polygon and Codeforces platforms.

Even though the contest is unrated, we believe it is an excellent way of practice, especially for Div 4 users.

Remember, if you don't know how to solve one problem, look at others!

UPD 1: Registration available now!

UPD 2: Round is over! We hope you enjoyed the problems and congratulations to the winners!

UPD 3: Editorial is out!

Div. 4 winners:

Not Div.4 Winners:

First to solve each problem:

A: First: Valera_Grinenko

Div. 4 first: anuragdvd

B: First: Geothermal

Div. 4 first: Esdeath_1

C: First: Geothermal

Div. 4 first: Esdeath_1

D: First: Geothermal

Div. 4 first: RamPrabodhInduri

E: First: Geothermal

Div. 4 first: -deleted-

F: First: IgorI

Div. 4 first: sahaun

• +244

By mesanu, history, 4 years ago,

This is the editorial for the Unofficial Div4 Round#1 created by SlavicG and mesanu.

Announcement

Previously you could only virtually participate, now the contest is open for practice!

Invitation link for the contest: https://mirror.codeforces.com/contestInvitation/d477e058f265a72092af5c11074234d720a0fb5f

PROBLEM A:

Alin and Money

PROBLEM B.

Sanda's Homework

Problem C:

Gicu's way Home

Problem D:

Game of GCD

Problem E:

Strange Pool
• +10