Hello Codeforces!

We are excited to invite you to join us on Saturday, May 16, and try the same fun yet challenging problems from Round 1 — VNOI CUP 2026!

• 🔈 Contest: https://oj.vnoi.info/contest/vnoicup26_r1_mirror
• 📅 Time: May 16, 2026 — 20:30 (GMT+7)

If you are Vietnamese and eligible to participate in the official round, we strongly encourage you to register and compete there instead.

This year, we also plan to invite a few top international participants from the unofficial mirror rounds to join the Final Round onsite in Vietnam. These participants will compete in the Open Division of the Final Round — a separate onsite leaderboard from the official Vietnamese contestants.

⚠️ Please note: invited participants from the Open Division will need to cover their own travel and accommodation expenses. However, VNOI will assist with hotel booking to make logistics easier for you.

VNOI CUP is a Competitive Programming competition hosted by VNOI (Vietnam Olympiads in Informatics community), a group of Vietnamese programmers working together to make programming competitions more fun and challenging in Vietnam. We're a non-profit organization dedicated to supporting the growth of competitive programming in Vietnam, and this competition is one of the many ways we aim to achieve that goal.

A huge shoutout to our awesome problem setters and testers! Thanks to their hard work, we have an exciting and high-quality problem set ready for you.

• Setters: Kuroni, Namine, bachbeo2007, darkkcyan, hihihaha, huyhasun, i_love_huyhau6a2, xuanquang1999, MofK, vinfat
• Testers: conqueror_of_tourist, awoo, shinchankosen, WataHata

VNOI CUP 2026 will consist of two online qualification rounds followed by an onsite Final Round. The qualification rounds will each last 3 hours and feature 7 problems. Based on the results, the top Vietnamese contestants will advance to the Final Round, which is expected to be held onsite in July 2026.

• Qualification Round 1: May 16, 2026 — 20:30 (GMT+7)
• Qualification Round 2: May 30, 2026 — 20:30 (GMT+7)
• Final Round (Onsite): July 2026 (exact date TBA)

As in previous years, the competition will be used with multiple subtasks with partial scoring, and penalty time based on incorrect submissions.

• Scoring: Each problem includes several subtasks with different constraints and point values. You must pass all test cases in a subtask to earn its points.
• Penalty Time: Equals the time of your last score-increasing submission for each problem, plus 5 minutes for each incorrect submission.
• Ranking: Determined by total score (descending). Ties will be broken by lower total penalty time.

⚠️ Each participant must only use one VNOJ account. Anyone who is found using multiple accounts will be disqualified and may be banned from future contests.

⚠️ Please refrain from using AI assistance tools during the contest. While the unofficial round is not subject to the same enforcement measures as the official round, we ask all participants to respect the spirit of fair competition.

We hope you enjoy the contest and wish all participants the best of luck! 🚀

• 🔈 Contest: https://oj.vnoi.info/contest/vnoicup26_r1_mirror
• 📅 Time: May 16, 2026 — 20:30 (GMT+7)
• 💻 Platform: VNOJ (online)
• 📜 Rules: https://s.vnoi.info/vnoi-cup-2026-rule-cf
• 🌏 Facebook: https://www.facebook.com/vnoi.wiki
• 📡 Discord: https://discord.gg/QUK2Tgr
• ⏲ VNOI Forum: https://www.facebook.com/groups/VNOIForum