what is the name of the episode whose number of the series episode was 31?
CREATE TABLE "table1_228973_3" (
  "no_in_series" real,
  "no_in_season" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text
);
SELECT "title" FROM "table1_228973_3" WHERE "no_in_series"=31;