Don't want to keep a running account, let's summarize the reasons for the test. .
$day1$：
$12$ to know what $t3$ does.
It can be done with tolerance + dynamic $dp$, but I don't have time to write it.
In fact, this method is also more complicated, and the calculation is much more elegant than this.
So it is still too slow to think, and you must have a clear mind in future exams.
$day2$：
$t1$ is a positive solution, not as violent as $AC$.
$t3$ misread the question and thought it was a random path of $n-1$, so it broke zero.
Common mistakes in exams are concentrated in one day, leading to retirement.
However, it is not completely dead, there is still a glimmer of hope to go to the national competition.
After reading the question, you must point to each word with your finger, and read the question three times before thinking.
Be sure to write and shoot, no matter what the question is (there are large samples that can be considered not to write).
Overturned the cart once, I hope not to repeat the same mistakes in the future.