Skip problem AB for this round.
C2. k-LCM (hard version)
Simple construction problem. The point is $\frac{n}{2}$. After dividing by 2, LCM is $\frac{n}{2}$. Then we just think of a way to subtract one, and make it can divide 2.
![](https://codeforces.org/s/38252/android-icon-192x192.png)
D. Genius
Normal. Know it's DP at very beginning. The memory limit is telling you it state compression DP directly.
The breakthrough point is: if just move forward, no need skip any questions.
And the IQ is only related to i and j. So it's safe to move backward.
The last issue is the case of same tag. Or state compression. Just normal things.
![](https://codeforces.org/s/38252/android-icon-192x192.png)
E2. Square-free division (hard version)
I not solved this problem by myself. I looked some others' solution.
I found the way to calculate the left, also thought about the dp definition. But not calculate dp successfully. So Sad.
I was trying to find some $O(n\cdot{k})$ solution. Because it need 4000,000 times calculation. And think may get TLE for $O(n\cdot{k})$ solution.
But after looked others' solution, $O(n\cdot{k^2})$ solution is ok. Then fine...
![](https://codeforces.org/s/38252/android-icon-192x192.png)