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Balkan MO
2018 Balkan MO
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2018 Balkan MO
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(1)
Balkan Mathematical Olympiad 2018 p3
Source: BMO 2018
5/9/2018
Alice and Bob play the following game: They start with non-empty piles of coins. Taking turns, with Alice playing first, each player choose a pile with an even number of coins and moves half of the coins of this pile to the other pile. The game ends if a player cannot move, in which case the other player wins.Determine all pairs
(
a
,
b
)
(a,b)
(
a
,
b
)
of positive integers such that if initially the two piles have
a
a
a
and
b
b
b
coins respectively, then Bob has a winning strategy.Proposed by Dimitris Christophides, Cyprus
conics
combinatorics