What episode number in the series had 2.77 million U.S. viewers?
CREATE TABLE "table1_24319661_5" (
  "no_in_series" real,
  "no_in_season" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "u_s_viewers_million" text,
  "original_air_date" text,
  "production_code" text
);
SELECT MAX("no_in_series") FROM "table1_24319661_5" WHERE "u_s_viewers_million"='2.77';