user: Question: What is the lowest rank of Citigroup?
Columns: ['Rank', 'Name', 'Headquarters', 'Industry', 'Market value ( USD million)']
Types: ['real', 'text', 'text', 'text', 'real']
Sample row: [1.0, 'Exxon Mobil', 'United States', 'Oil and gas', 371631.0]
SQL:

assistant: SELECT MIN("Rank") FROM "Table" WHERE "Name" = 'Citigroup';