SCHEMA:
CREATE TABLE table_28538368_2 (mountains_classification VARCHAR, winner VARCHAR, general_classification VARCHAR, points_classification VARCHAR)
USER:
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?

QUERY:
SELECT mountains_classification FROM table_28538368_2 WHERE general_classification = "Alberto Contador Kanstantsin Sivtsov" AND points_classification = "Alessandro Petacchi" AND winner = "Mark Cavendish"