How many seasons was the losing team Adelaide City?
CREATE TABLE "nsl_cup_winners" (
  "season" text,
  "cup_final_date" text,
  "winning_team" text,
  "score" text,
  "losing_team" text,
  "location" text,
  "cup_final_attendance" real
);
SELECT COUNT("season") FROM "nsl_cup_winners" WHERE "losing_team"='Adelaide City';