Problem

Source: Portugal OPM 2023 p6

Tags: combinatorics, combinatorial geometry



A rectangular board, where in each square there is a symbol, is said to be magnificent if, for each line$ L$ and for each pair of columns $C$ and $D$, there is on the board another line $M$ exactly equal to $L$, except in columns $C$ and $D$, where $M$ has symbols different from those of $L$. What is the smallest possible number of rows on a magnificent board with $2023$ columns?