We started about 50 mins after the contest had begun.

#I AC 61 mins

Brute force

#E AC 105 mins

Greedy

#A AC 113 mins 2 wrong tries by WHD

#C AC 126 mins 1 wrong try

AC automation

#H AC 153 mins 1 wrong try

Math

#F AC 224 mins 1 wrong try

Game theory

#B AC 259 mins 5 wrong tries

The solution for this problem is first written by WHD. I rewrote it and got AC after 1 wrong try.

#J AC 284 mins 4 wrong tries by WHD

WHD used a right algorithm to solve this problem, but made a small mistake. After I found it out, WHD corrected it and got AC.