$4$
12. (5 points)
Fairy has a magic wand that can turn “death” into “life” or “life” into “death” with one wave. One day, Fairy saw 4 trees, 2 of which were already withered, as shown in the figure below. She waved her magic wand, hoping all the trees would be in a “living” state, but unfortunately, the magic wand malfunctioned and not only affected the tree she pointed at but also the adjacent trees. How many times does she need to wave the magic wand at least to fulfill her wish?