Table: list of tallest buildings in the european union
Question: How many buildings in the European Union were once the tallest, but no longer hold that title?
Step 1 (Operation, Indexing): years as tallest
Step 2 (Reasoning, Grounding): once the tallest, but no longer hold, not until present
Step 3 (Operation, Filter): years as tallest
Step 4 (Reasoning, Aggregating): COUNT, number of buildings
Answer: 6