Hi everyone!

As the last ICPC contest in the Asia-East continent, the participators of EC-final are advanced from several regionals based on their outstanding performance. 2019 ICPC Asia-East Continent Final ended on 15 Dec 2019, hosted by Northwestern Polytechnical University, Xi'an, Shannxi Province, China. This year, there are 386 teams gathered in Xi'an fighting for the unique championship. We are really impressed by their programming skills and perfectionism.

The problems are mainly prepared by the former ICPC members from Tsinghua University and Shanghai Jiao Tong University. We've added all problem sets in Gym. We are glad to invite you to participate in the mirror contest through 2019 ICPC Asia-East Continent Final. You can click on the virtual participation button and start to solve the problems whenever you want. We haven't gotten ghosts yet. We will add it ASAP when they are ready.

Many thanks to

• volunteers and staffs from Northwestern Polytechnical University for your hospitality;

• ICPC committee for your guidance and technique support;

• Problem authors: littlelittlehorse, jqdai0815 and xyz2606 for your outstanding work.

• Testers: yasugongshang, WZYYN, Rewinding, Rebelz, A.K.E.E., TianyiQ and ztxz16 for your proofreading.

• Codeforces community for your algorithm-learning atmosphere and super powerful problem preparing system — polygon.

Without any of you, this contest couldn't be such successful.

Hope you a wonderful coding experience during the contest. Any suggestions or questions are welcomed.