And one more solution for D: 41376803 It has O(2²ⁿ + q * n) complexity and the most interesting part — it doesn't use that k is relatively small.

First, as in mouse_wireless's solution, we want to count Wu value for all possible masks and create a vector pre_w containing pairs (Wuvalue, mask). Then we sort this vector in increasing order and now we are ready to another precalc)

For each possible string t we build a vector based on pre_v: we just change mask to (), which will represent s string needed to get this mask. Now we have to iterate over new vector once again to do following: we will change second value in every pair (ex-mask and ex-()) to number of string in S, for which Wuvalue doesn't exceed current Wuvalue (in current pair). We can do this by simple dp.

Now, for answering a query, all we need is binary search a vector related to given t. It is the part which has a O(q * n) complexity.

Unfortunately, during the contest I got TL4 with this solution beacause of slow IO. Thanks to SHAMPINION, who advised me to add two stirngs of code, which make IO faster and after that the solution passed in 1.7 s.

If one can solve all the problems, will he be hired by Elon Musk?

And.. here another post which has over 100 upvotes is

Is it OK if a contestant from my city (Izhevsk) has received a t-shirt 4 days ago, but I still haven't?

I beware to say a wrong thing, but I think I could prove that if we fix some point of convex hull, then take two points next to the fixed one clockwise, we should do such process:
1. move the furthest point (from fixed clockwise) clockwise, if it will increase area of traingle
2. else move the closest point clockwise, if it will increase area of triangle
If both actions will decrease square, we have found the maximum area of triangle containing the fixed point.
Applying that to all points takes N².

The same thing to me)

I've surprisingly found mine in a spam folder.

Nice example of how are Russian and Polish close

So why the complexity is not O(n log n)?

Unfortunately, I haven't learnt how to write formulas in comments yet.

In 639D - Bear and Contribution, that does "iterate over possible values of x from lowest to highest" mean? Don't we need to sort all these values first?