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 (laps INTEGER, driver VARCHAR, grid VARCHAR)
### Question:
what's the highest lap that contains the driver of graham hill and a grid that is larger than 18?
### Answer:
SELECT MAX(laps) FROM table_name_34 WHERE driver = "graham hill" AND grid > 18