Changed initial code to this:

-- You will be given a table 'kata' with columns 'id', 'n', 'x', and 'y'. 
-- Return the 'id' and your result in a column named 'res' using a SELECT statement.
-- You DON'T need to create a function, that's for other languages.
select * from kata

Is that clearer now?

The desciption is for all languages. Since SQL is somewhat special you are not forced to write a function but it is sufficient to write a query resulting in the desired output.