Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_name_31 ( constructor VARCHAR, laps VARCHAR, grid VARCHAR )

### Question ###
Who was the constructor of the car that went 56 laps and had a grid of 15?

### Accurate SQL ###

SELECT constructor FROM table_name_31 WHERE laps = "56" AND grid = "15"