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_25721_3 (episode_no INTEGER, airdate VARCHAR)
### Question:
Which episode number aired on 18 october 2012?
### Answer:
SELECT MIN(episode_no) FROM table_25721_3 WHERE airdate = "18 October 2012"