Write SQL query to solve given problem: How many dishes are there on page 1 of menu ID12882?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT SUM(CASE WHEN T1.page_number = 1 THEN 1 ELSE 0 END) FROM MenuPage AS T1 INNER JOIN MenuItem AS T2 ON T1.id = T2.menu_page_id WHERE T1.menu_id = 12882