Question: The KVLY-TV mast is the fourth tallest structure in the world behind the megatall skyscraper that is how many stories in height?
Sentence (from "KVLY-TV mast"): Completed in 1963, it was the tallest structure in the world until succeeded by the Warsaw radio mast in 1974, which collapsed in 1991, again making the KVLY-TV mast the tallest structure in the world until the Burj Khalifa overtook it in 2010.
Relevant evidence: No