How many main actors are there in the movie Pirates of the Caribbean: At World's End?
main actors refers to gender = 'male' and min(cast_order); Pirates of the Caribbean: At World's End refers to title = 'Pirates of the Caribbean: At World''s End'
SELECT COUNT(T2.cast_order) FROM movie AS T1 INNER JOIN movie_cast AS T2 ON T1.movie_id = T2.movie_id INNER JOIN gender AS T3 ON T3.gender_id = T2.gender_id WHERE T3.gender = 'Male' OR T3.gender = 'Female' AND T1.title = 'Pirates of the Caribbean: At World''s End' AND T2.cast_order = ( SELECT MIN(T2.cast_order) FROM movie AS T1 INNER JOIN movie_cast AS T2 ON T1.movie_id = T2.movie_id INNER JOIN gender AS T3 ON T3.gender_id = T2.gender_id WHERE T3.gender = 'Male' OR T3.gender = 'Female' AND T1.title = 'Pirates of the Caribbean: At World''s End' )