Write SQL query to solve given problem: Provide the total number of the male users that use OPPO as their phone brand.. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT COUNT(T1.device_id) FROM gender_age AS T1 INNER JOIN phone_brand_device_model2 AS T2 ON T1.device_id = T2.device_id WHERE T2.phone_brand = 'OPPO' AND T1.gender = 'M'