Problem

Source: Saint Petersburg MO 2020 Grade 11 Problem 2

Tags: combinatorics



A short-sighted rook is a rook that beats all squares in the same column and in the same row for which he can not go more than $60$-steps. What is the maximal amount of short-sighted rooks that don't beat each other that can be put on a $100\times 100$ chessboard.