Write SQL query to solve given problem: What is the difficulty of the course in which a student with level of intellengence of 5 got an A grade?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT T3.diff FROM student AS T1 INNER JOIN registration AS T2 ON T1.student_id = T2.student_id INNER JOIN course AS T3 ON T2.course_id = T3.course_id WHERE T2.grade = 'A' AND T1.intelligence = 5