MathDB
Letters in grid

Source: CGMO 2016 Q6

August 14, 2016
combinatorics

Problem Statement

Find the greatest positive integer mm, such that one of the 44 letters C,G,M,OC,G,M,O can be placed in each cell of a table with mm rows and 88 columns, and has the following property: For any two distinct rows in the table, there exists at most one column, such that the entries of these two rows in such a column are the same letter.