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_1831309_1 (length_of_mandatory_secondary_school INTEGER)
### Question:
What is the longest length of mandatory secondary school?
### Answer:
SELECT MAX(length_of_mandatory_secondary_school) FROM table_1831309_1