Kvant Math Problem 2873

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Verdicts: FAIL + FAIL
Solve time: 39m12s
Source on kvant.digital

Problem

A natural number $n$ is given. A regular hexagon with side $n$ is divided into $6n^2$ small equilateral triangles of side 1. A row is the set of triangles between two consecutive parallel lines of the subdivision. Petya has placed a chip on some of the triangles. Vasya needs to remove no fewer than 0 and no more than $k$ chips so that each of the $6n$ rows contains an even number of chips. What is the minimum $k$ for which he can guarantee this?

I. Bogdanov

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