Difference between revisions of "2014 USAMO Problems/Problem 4"
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Revision as of 16:44, 30 April 2014
Problem
Let be a positive integer. Two players
and
play a game on an infinite grid of regular hexagons. Initially all the grid cells are empty. Then the players alternately take turns with
moving first. In his move,
may choose two adjacent hexagons in the grid which are empty and place a counter in both of them. In his move,
may choose any counter on the board and remove it. If at any time there are
consecutive grid cells in a line all of which contain a counter,
wins. Find the minimum value of
for which
cannot win in a finite number of moves, or prove that no such minimum value exists.