
Hello, if you look at the above image, you''ll see that I have identified what I believe to be a skyscraper with those four green 3's. Those two red 3's see both ends of the skyscraper and are the ones that should be removed. Everything looks right to me but it's wrong. The lower red 3 is an actual 3 and shouldn't be removed, therefore I don't know what I'm doing

Why isn't that a skyscraper?
Thanks