-- Database schema
| course : course_id [ INTEGER ] primary_key , name [ TEXT ] , credit [ INTEGER ] , diff [ INTEGER ] | prof : prof_id [ INTEGER ] primary_key , gender [ TEXT ] , first_name [ TEXT ] , last_name [ TEXT ] , email [ TEXT ] , popularity [ INTEGER ] , teachingability [ INTEGER ] , graduate_from [ TEXT ] | RA : student_id [ INTEGER ] RA.student_id = student.student_id , capability [ INTEGER ] , prof_id [ INTEGER ] RA.prof_id = prof.prof_id , salary [ TEXT ] | registration : course_id [ INTEGER ] registration.course_id = course.course_id , student_id [ INTEGER ] registration.student_id = student.student_id , grade [ TEXT ] , sat [ INTEGER ] | student : student_id [ INTEGER ] primary_key , f_name [ TEXT ] , l_name [ TEXT ] , phone_number [ TEXT ] , email [ TEXT ] , intelligence [ INTEGER ] , gpa [ REAL ] , type [ TEXT ] |
-- -- What is the difficulty of the course in which a student with level of intellengence of 5 got an A grade?

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;