Arrows in cells
Source: St Petersburg Olympiad 2018, Grade 9, P7
July 13, 2018
combinatorics
Problem Statement
In square we choose cells. In every chosen cell we draw one arrow from the angle to opposite angle. It is known, that for any two arrows, or the end of one of them coincides with the beginning of the other, or
the distance between their ends is at least 2. What is the maximum possible value of ?