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Socialists Republic Of Czechoslovakia 10

Source: IMO LongList 1959-1966 Problem 45

September 2, 2004
combinatoricsmaximizationExtremal combinatoricsCombinatorics of wordsIMO ShortlistIMO Longlist

Problem Statement

An alphabet consists of nn letters. What is the maximal length of a word if we know that any two consecutive letters a,ba,b of the word are different and that the word cannot be reduced to a word of the kind abababab with aba\neq b by removing letters.