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 STUDENT (city_code VARCHAR)
### Question:
What is the city_code of the city that the most students live in?
### Answer:
SELECT city_code FROM STUDENT GROUP BY city_code ORDER BY COUNT(*) DESC LIMIT 1