The main purpose of this contest is to give an opportunity to Japanese delegations and candidates of delegations for training and practice for IOI. But the contest itself is open to everybody. Everybody is welcome to attend JOI Open Contest 2018!
The contest duration is 5 hours and there will be 4 problems. Each submitted source program must be written in either C++, Pascal, or Java. Problem statements will be provided both in Japanese and English.
Details are available in contest information.
The past contest information is available in JOI Website.
Good luck and have fun!
UPD1 I uploaded the editorials, sample source codes, and input/output data in the contest information page.