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Mary and Pat play a number game, smallest initial integer for Pat not winning

Source: Irmo 2018 p1 q1

September 16, 2018
game strategygamenumber theoryminimum

Problem Statement

Mary and Pat play the following number game. Mary picks an initial integer greater than 20172017. She then multiplies this number by 20172017 and adds 22 to the result. Pat will add 20192019 to this new number and it will again be Mary’s turn. Both players will continue to take alternating turns. Mary will always multiply the current number by 20172017 and add 22 to the result when it is her turn. Pat will always add 20192019 to the current number when it is his turn. Pat wins if any of the numbers obtained by either player is divisible by 20182018. Mary wants to prevent Pat from winning the game. Determine, with proof, the smallest initial integer Mary could choose in order to achieve this.