Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE table_name_21 (stage VARCHAR, general_classification VARCHAR, winner VARCHAR)
### Question:
What is the stage of winner Carlos Sastre when the general classification was Denis Menchov?
### Answer:
SELECT stage FROM table_name_21 WHERE general_classification = "denis menchov" AND winner = "carlos sastre"