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_203_515 ( id number, "rank" number, "city" text, "passengers" number, "ranking" number, "airline" text )

### Question ###
how many more passengers flew to los angeles than to saskatoon from manzanillo airport in 2013 ?

### Accurate SQL ###

SELECT (SELECT "passengers" FROM table_203_515 WHERE "city" = 'los angeles') - (SELECT "passengers" FROM table_203_515 WHERE "city" = 'saskatoon')