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I have impressive achievements such as the top6 of Belarus on Codeforces.com, the winner of Ukrainian Olympiad in Informatics, the winner of anime quis in SIS. I love russian phonk. My friends call me bebrochka.

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A lot of time has passed since the end of these rounds. I and other users codeforces want to have task ratings for effective practice. Please, can rate problems CF Rounds 845 & 846.

How to solve 2 dimesional subset sum problem elegant?

2 dimesional subset sum is: You give $$$n$$$ pairs $$$x_i$$$, $$$y_i$$$, choose any $$$k$$$ elements that $$$x_1+x_2+...+ x_k = 0$$$ and $$$y_1+y_2+...+ y_k = 0$$$.

I can solve this only with dp on O($$$n^3$$$ $$$\cdot$$$ $$$c^2$$$), where $$$n$$$ — count elements and $$$c$$$ — max $$$x$$$ or $$$y$$$ element, and with bitset get optimaze on divide time to $$$64$$$. Also I can solve using meet-in-the-middle. Are all these solutions 2-d subset sum?