Shrinking List Puzzle
The first \( 9 \) natural numbers are given in a list. You are supposed to select two numbers randomly from the list, call them \( x \) and \( y \), remove them from the list and insert \( x + y + xy \) into the list. You keep repeating this until you are left with only one number in the list. Find the final number that is left in the list.
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