Hello, Codeforces!

The 2019-2020 ICPC Asia Hong Kong Regional Contest has ended on December 1. Due to the recent social movements in the city, the campus of the City University of Hong Kong, where the contest was originally planned to be hosted, sustained damage and was closed. It was decided to hold the contest in Shenzhen, China instead two weeks before the contest. The contest was eventually successfully conducted in the National Supercomputing Center in Shenzhen. Thirty-eight teams (including two unofficial middle school teams) from China, Hong Kong SAR and Macau SAR participated in the onsite contest. Team CodeChant from Zhongshan (Sun Yat-sen) University won the contest who solved 6 of the 11 problems. However, the contest is actually not that hard. Some strong teams in China were not able to participate in the contest because many universities in mainland China blocked all visits to Hong Kong on political grounds, while some others voluntarily chose not to go due to safety concerns.

The problems for this contest were prepared by retired ICPC participants of Zhejiang University, and I was the coordinator of the problem-setting group. We are glad to announce that we have published the contest, 2019-2020 ICPC Asia Hong Kong Regional Contest in Codeforces::Gym for you to practice. Feel free to start virtual participation or to solve the problems individually. For virtual participation, the contest is 5 hours in length and follows usual ICPC rules. Team participation is recommended, but it is also possible to participate individually. The ghosts of the onsite participants are available, you may take advantage of it.

My thanks go to:

• The RCD, Dr. Minming Li from City University of Hong Kong and staff from National Supercomputing Center in Shenzhen for their tireless efforts in hosting the contest successfully under difficult circumstances.

• Problem authors: lsmll, Claris, jiangshibiao, shb123, reku, lzw4896s, J.T.J.L., lqybzx and Sugar_fan.

• Testers: chenjb, oipotato, Subconscious, chenyanbo and two other members of Zhejiang University ICPC team.

• MikeMirzayanov for the Codeforces platform and the Polygon system where we prepared the problems.

We have prepared an English editorial. Hope you enjoy the problems and feel free to discuss them in the comments.