CREATE TABLE table_56657 ("Home team" TEXT, "Home team score" TEXT, "Away team" TEXT, "Away team score" TEXT, "Venue" TEXT, "Crowd" FLOAT, "Date" TEXT)

What is the smallest crowd of the away team that scored 12.9 (81)?
SELECT MIN("Crowd") FROM table_56657 WHERE "Away team score" = '12.9 (81)'
SELECT MIN("Crowd") FROM "table_56657" WHERE "Away team score" = '12.9 (81)'