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MathNet 2013 Question 74

Math Olympiad Vault · MathNet 2013

Question 74

Numbers $1, \dots, 200$ are written on a blackboard in one line. Juku has to write in front of each number plus or minus sign so that for any positive integer $n \le 100$ the number itself and one of its multiples have different signs. Which numbers must he assign a minus sign in order to get the maximal possible value of the expression?