How many episode air dates are there for auditioning city Rio De Janeiro?
CREATE TABLE "regional_auditions" (
  "episode_air_date" text,
  "audition_city" text,
  "audition_date" text,
  "audition_venue" text,
  "guest_fourth_judge" text
);
SELECT COUNT("episode_air_date") FROM "regional_auditions" WHERE "audition_city"='Rio de Janeiro';