Changes to contest/acm/POJ/1690

• 2023-06-30 01:02:57 UTC (jserv): Revert to abb6af95d6bc98ac651e2fb0fd79fe0f0a9b2d00
• 2023-06-29 08:31:44 UTC (wjhtnpd): .
• 2013-01-06 08:03:38 UTC (free999): 注意的點