What was the format for the 4 disc season that had less than 22 episodes and n/a for region 4?
CREATE TABLE "dvd_and_blu_ray_releases" (
  "dvd_season" text,
  "format" text,
  "num_episodes" real,
  "num_disc_s" real,
  "region_4" text
);
SELECT "format" FROM "dvd_and_blu_ray_releases" WHERE "num_episodes"<22 AND "num_disc_s"=4 AND "region_4"='n/a';