A bug was fixed in the checker program that incorrectly skipped most of the checks for some tests. The most affected tests are: 1, 3-8, 11, 17.

All solutions have been rejudged. The verdict changed for 40% of solutions (typical change patterns: WA5 -> WA4, WA9 -> WA7, AC -> WA11). 10 authors lost the Solved status for the problem.