Y by
Albert and Brita play a game with a bar of
adjacent squares. Initially, there is a button on the middle square of the bar. At every turn Albert mentions one positive integer less than
, and Brita moves button a number of squares in the direction of her choice - while doing so however, Brita must not move the button more than twice in one direction order. Prove that Albert can choose the numbers so that by the
th turn, Brita to be forced to move the button out of the bar.


