Who wrote the episodes watched by 1.816 million people in Canada?
CREATE TABLE "table1_18424435_3" (
  "no" real,
  "num" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "canadian_air_date" text,
  "u_s_air_date" text,
  "production_code" real,
  "canadian_viewers_million" text
);
SELECT "written_by" FROM "table1_18424435_3" WHERE "canadian_viewers_million"='1.816';