How many semi-final weeks are there for acts from Pittsburgh, Pennsylvania?
CREATE TABLE "round_chart" (
  "name_name_of_act" text,
  "age_s" text,
  "genre" text,
  "act" text,
  "hometown" text,
  "qtr_final_week" real,
  "semi_final_week" text,
  "position_reached" text
);
SELECT COUNT("semi_final_week") FROM "round_chart" WHERE "hometown"='Pittsburgh, Pennsylvania';