Table: dvd_season_info
Columns: dvd_season
format
episodes
disc_s
region_4

Question: What was the format for the 4 disc season that had less than 22 episodes and n/a for region 4?
SQL: SELECT "format" FROM dvd_season_info WHERE "episodes" < 22 AND "disc_s" = 4 AND "region_4" = 'n/a'