Who is the director of the episode at entry number 13? 
CREATE TABLE "table1_15026994_3" (
  "num" real,
  "episode" text,
  "writer" text,
  "director" text,
  "original_air_date" text,
  "viewing_figure" text
);
SELECT "director" FROM "table1_15026994_3" WHERE "num"=13;