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_202_135 ( id number, "series" number, "year" text, "rank" text, "average audience share" text )

### Question ###
how many years did heartbeat series run in total ?

### Accurate SQL ###

SELECT MAX("year") - MIN("year") FROM table_202_135