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Alberto plays a game for Barbara's birthday

Source: Italian National Olympiad 2007, problem 4

May 13, 2007
linear algebramatrixcombinatorics proposedcombinatorics

Problem Statement

Today is Barbara's birthday, and Alberto wants to give her a gift playing the following game. The numbers 0,1,2,...,1024 are written on a blackboard. First Barbara erases 292^{9} numbers, then Alberto erases 282^{8} numbers, then Barbara 272^{7} and so on, until there are only two numbers a,b left. Now Barbara earns ab|a-b| euro. Find the maximum number of euro that Barbara can always win, independently of Alberto's strategy.