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MathNet 2025 — Part 01 (100 complete bilingual questions) Question 72

Math Olympiad Vault · MathNet 2025 — Part 01 (100 complete bilingual questions)

Question 72

Numbers $1, 2, 3, \ldots, 60$ are written in a row (in this order). Igor and Ruslan take turns in making moves; Igor starts; by one move the player puts one of the signs of operation $+$, $-$, $\times$ between some pair of adjacent numbers. When a sign is placed between every two adjacent numbers we calculate the value of the obtained expression. Igor wins if this value is divisible by $3$, otherwise Ruslan wins. Determine who of the two players has a winning strategy.