CREATE TABLE table_45956 ("Rider" CLOB, "Manufacturer" CLOB, "Laps" FLOAT, "Time" CLOB, "Grid" FLOAT)

Which Grid has Laps of 24, and a Rider of marco melandri?
SELECT SUM("Grid") FROM table_45956 WHERE "Laps" = '24' AND "Rider" = 'marco melandri'
SELECT SUM("Grid") FROM "table_45956" WHERE "Laps" = '24' AND "Rider" = 'marco melandri'