On how many different dates did the episode directed by Marcos Siega and written by Scott Buck air for the first time?
create table table_24132083_1 (original_air_date varchar, directed_by varchar, written_by varchar, PRIMARY KEY (original_air_date))
select count(original_air_date) from table_24132083_1 where directed_by = "marcos siega" and written_by = "scott buck"