JOI Open Contest 2018

This is an IOI-like open competition for students at schools for secondary education. The main purpose of this contest is to give an opportunity to Japanese delegations and candidates of delegations for training and practice. But the contest itself is open to everybody. Everybody is welcome to attend JOI Open Contest 2018!

The duration of the contest is 5 hours. The same contests are held twice (Round 1 and Round 2). Contestants can participate in one of Round 1 or Round 2 according to their time zone. After Round 2 finishes, we will open the judging server for one day. Interested contestants can improve and resubmit their solutions by themselves.

Registration will be open before each contest. A link to the registration page will appear on this page about 30 minutes before the beginning of each contest. Contestants can register on the contest site by themselves from the right before the beginning of each contest until the end of it.

No prizes will be given to the contestants.

Contest Information

JOI Open Contest 2018
Contest System
Contest duration
5 hours
The number of tasks
4 tasks
English, Japanese
Round 1
Sunday, July 8, 2018
13:00-18:00 13:15-18:15 +0900 (JST)
04:00-09:00 04:15-09:15(UTC/GMT)
Round 2 (tasks for Round 1 and Round 2 are the same)
Sunday, July 8, 2018
19:00-24:00 +0900 (JST)
10:00-15:00 (UTC/GMT)


Rules that are same as IOI 2017 Rule:

Rules that are not same as IOI 2017 Rule:

Contet Site


Problem Statements


Sample Sources

Test Data

Problem inventors


Please answer the questionnaire. We appreciate your feedback on our contest!


joiopen at


Creative Commons License
The tasks for JOI Open Contest 2018 by JCIOI (the Japanese Committee for the IOI) is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License. If you need a license other than a Creative Commons Attribution-ShareAlike 4.0 International License (CC BY-SA 4.0), please ask JCIOI.