user: ### NOW ANSWER:
Question: Tell me the sum of laps with a time/retired of +13 laps with grid more than 18
Columns: ['Driver', 'Constructor', 'Laps', 'Time/retired', 'Grid']
Types: ['text', 'text', 'real', 'text', 'real']
Sample row: ['Alberto Ascari', 'Ferrari', 80.0, '2:42:39.3', 3.0]
SQL:

assistant: SELECT SUM("Laps") FROM "Table" WHERE "Time/retired" = '+13 laps' AND "Grid" > 18.0;