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IL-GILLIS 2023 Problem 7

    Ana and Banana are playing a game. Initially, Ana secretly picks a number 1≤A≤1061\leq A\leq 10^6 . In each subsequent turn of the game, Banana may pick a positive integer BB , and Ana will reveal to him the most common digit in the product A⋅BA\cdot B (written in decimal notation). In the case when at least two digits are tied for being the most common, Ana will reveal all of them to Banana. For example, if A⋅B=2022A\cdot B=2022 , Ana will tell Banana that the digit 22 is the most common, while if A⋅B=5783783A\cdot B=5783783 , Ana will reveal that 3,73, 7 and 88 are the most common. Banana's goal is to determine with certainty the number AA after some number of turns. Does he have a winning strategy?

    Dataset text AI-MO AoPS. Quoted with source.

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