user: Question: What is the smallest height (ft) of a building in frankfurt with a height (m) of 257 and less than 55 floors?
Columns: ['Name', 'City', 'Height (m)', 'Height (ft)', 'Floors', 'Years as tallest']
Types: ['text', 'text', 'real', 'real', 'real', 'text']
Sample row: ['Commerzbank Tower', 'Frankfurt', 259.0, 850.0, 56.0, '1997–present']
SQL:

assistant: SELECT MIN("Height (ft)") FROM "Table" WHERE "City" = 'frankfurt' AND "Height (m)" = 257.0 AND "Floors" < 55.0;