Dear Codeforces community,

Lately, we have successfully organized a high-schoolers' contest: HNOI Civil War. The contest was born as a "rivalry" between two of the best Hanoi-based gifted high schools: Hanoi-Amsterdam High School and Nguyen Hue High School. 3-people organizing committee includes: Trung Lan Nguyen (lantrungseo) — as the Head Organizer, Bao Quoc Ngo (b21quocbao) — as the Head Problemsetter and coach for Nguyen Hue informatics team for this contest, and me, Dung Tuan To low_ — as the Head Coordinator and coach for Hanoi-Amsterdam team.

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The competition consists of two contests: an Individual-based OI-formatted round and a Team-based ACM-formatted round. You can visit the rounds as information listed below:

• Individual Round One (July 14): written by low_ and lantrungseo, consists of 4 OI problems: HCW 19 Individual Day 1.

• Individual Round Two (July 14): written by b21quocbao, consists of 3 OI problems: HCW 19 Individual Day 2

(The onsite participants were only allowed to submit once after the end of the contest — just like a mock test of Vietnamese Olympiads in Informatics. All problem statements from these OI contests are in Vietnamese. You can request English statements in my Email, but don't expect it to be fast)

• Team Round (July 21): written by low_, lantrungseo and b21quocbao, consists of 12 ACM-based problems (we rate it as a 3-star gym round by ourselves): HCW 19 Team Round (ICPC format). Statements of this round are in English, so you can easily virtual participate and try if you can solve all the problems.

Here are the results:

Individual Rounds:

(Tan Trinh (tan472002) — winner of Individual Rounds — posing with coach Bao Ngo (left) and opposing coach Dung To (right) )

First Prize: Tan Huu Trinh (tan472002) from Nguyen Hue High School.

Second Prize: Dong Quang Le (CNH_Tourist) from Nguyen Hue High School.

Third Prize: Dat Quoc Ngo (datr1bs) and Nam Hai Do-Nguyen (NamSPro), both from Hanoi-Amsterdam High School.

Best Lower-grader Performance (awards for best performance of students born in 2003 or later): Minh Duc Le (ld_minh4354), from Hanoi-Amsterdam High School (He is the youngest of the whole contest: just a 10th grader!).

Team Round:

(Ams.TRIGGER — winner of Team Round — posing with Head Organizer Trung Nguyen (right) and coach of opposing school Bao Ngo (left) )

Winner: Ams.TRIGGER (Nam Hai Do-Nguyen NamSPro, Bach Gia Truong bachtruoq, and Phuc Linh Bui-Huy lienquanpc).

Best Lower-grader Performance: NH.Noob_Strike(Yaosu) (Dong Quang Le CNH_Tourist, Linh Hong Nguyen Chanchan, and Khoa Anh Nguyen-Viet darkness_peach).

So which school wins?

Each school performance is assessed by a scale of 1000: 70% of it comes from Individual Rounds and the other 30% comes from Team Round. The formula for each school is calculated as below, and only top 7 individuals and top 2 teams of each school are considered for this assessment:

int individualPoints=sumBest7Performances; //max point of each performance is 40 - same as VOI
int teamPoints=totalProblemCount2HighestRankedTeam*12.5-totalPenalties2HighestRankedTeam*0.02; //max point is 150 for each team
int finalPoint=individualPoints*2.5+teamPoints;

(I dunno how to put maths here ;-;)

So here is the result:

Hanoi-Amsterdam High School

Individual: 76.24

Team: 89.32

Total: 279.92

Nguyen Hue High School

Individual: 70.59

Team: 93.22

Total: 269.695

Close call at the end of the Team Round, but Hanoi-Amsterdam High School wins!!

Issues & Notes:

In the Individual Round: ldmhoang submitted two times after the contest ended. The first time he got a partial result of 0.00 point, but he changed his code in the submitting time (which is not allowed). The Organizing Comittee decided to deduct all points he earned (2.5) in this problem while calculating the result for him in awards and towards the final school points. But the official leaderboard on Codeforces still show the result of the second submission.

In the Team Round: there were several problems which has some issues regarding unclear statements. Those have been fixed immediately, and virtual participants can gym with this problemset without any issues.

There is a problem regarding weak tests in problem C. It has been fixed to public the contest. Although, two Accepted solutions in this problem (belong to NH.3chuphof and NH.Noob_Strike(Yaosu) ), which got WA afterwards, still count as accepted when we awarding prizes and assessing points for each school.

Thank you...

To two amazingly caring teachers: Thuy Thi Le and Hanh Hong Nghiem-Thi of Hanoi-Amsterdam High School for sponsoring us to organize this competition.

To Nguyen Hue High School, and teachers Duong Thuy Do-Thi and Tung Thanh Nguyen for providing us with venue to hold this contest.

To Codeforces server (MikeMirzayanov) for the gym platform. We had great time holding a gym contest here. We're also thankful for this not breaking down during contests times.

To Polygon for being an awesome platform for problemsetting.

To all participants for being there in the first season of this. You guys rock! Good luck to all of you in the next HNOI (Hanoi Olympiads in Informatics).

Thank you all for reading till here. Have a great day!

Oh, and I invite all of you to virtual participate in HCW 19 Team Round (ICPC format). This is the first time our team of three ever organized an ACM round. We honestly admit that we recycled some old problem in Gym (due to our lack of time preparing for this contest), but most of them are original, so you can try if you can solve all of 12 problems in 5 hours!

Winning school cup and editorial for Team Round will be here soon.