Xvii cono sur [argentina 2006] q4.
Source: Spanish Communities
May 11, 2006
combinatorics proposedcombinatorics
Problem Statement
Daniel writes over a board, from top to down, a list of positive integer numbers less or equal to 10. Next to each number of Daniel's list, Martin writes the number of times exists this number into the Daniel's list making a list with the same length. If we read the Martin's list from down to top, we get the same
list of numbers that Daniel wrote from top to down. Find the greatest length of the Daniel's list can have.