user: ### NOW ANSWER:
Question: Which Grid has Laps of 24, and a Rider of Marco Melandri?
Columns: ['Rider', 'Manufacturer', 'Laps', 'Time', 'Grid']
Types: ['text', 'text', 'real', 'text', 'real']
Sample row: ['Valentino Rossi', 'Yamaha', 24.0, '43:09.599', 4.0]
SQL:

assistant: SELECT SUM("Grid") FROM "Table" WHERE "Laps" = 24.0 AND "Rider" = 'Marco Melandri';