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Initially Billy is given two options "A-M" or "N-Z". By hitting the "right arrow", two nodes appear under "N-Z" further dividing the letters into "N-T" or "U-Z". This could continue until Billy ends up at only one letter, which would require 4-5 key presses. The design shown above below narrows down to three letter, at which point Billy could use the "left", "right", "select" keys to choose from one of three possible letters. After a letter is selected, the tree clears leaving only the first two choices.
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