Name the series number for  m. scott veach & rebecca kirsch
CREATE TABLE "table1_20704243_5" (
  "series_num" real,
  "season_num" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "u_s_viewers_in_millions" text
);
SELECT "series_num" FROM "table1_20704243_5" WHERE "written_by"='M. Scott Veach & Rebecca Kirsch';