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_34 (duration VARCHAR, start VARCHAR, stage VARCHAR, difficulty VARCHAR)
### Question:
How long does the one that stars with son bou of middle difficulty, and on a stage number larger than 13 last?
### Answer:
SELECT duration FROM table_name_34 WHERE stage > 13 AND difficulty = "middle" AND start = "son bou"