When Alberto Contador Kanstantsin Sivtsov was the general classification and Alessandro Petacchi was the points classification at the same time while Mark Cavendish is the winner, who was the mountain classification?
CREATE TABLE "classification_leadership" (
  "stage" real,
  "winner" text,
  "general_classification" text,
  "points_classification" text,
  "mountains_classification" text,
  "young_rider_classification" text
);
SELECT "mountains_classification" FROM "classification_leadership" WHERE "general_classification"='Alberto Contador Kanstantsin Sivtsov' AND "points_classification"='Alessandro Petacchi' AND "winner"='Mark Cavendish';