What is the Pinyin for the item that has a density of 77?
CREATE TABLE "administrative_divisions" (
  "name" text,
  "hanzi" text,
  "hanyu_pinyin" text,
  "population_2010_11_01" text,
  "area_km" text,
  "density_km" text
);
SELECT "hanyu_pinyin" FROM "administrative_divisions" WHERE "density_km"='77';