Core Data Many To Many Relations

i have a problem with iOS Core Data and many to many relations. I want to write a fitness application. So i need three tables. Following constuct:

Table Workout:

• id
• name

Table Practice:

• id
• name

Table Set

• id
• break

Now, each workout can have many practices. And each practice can be in different workouts. Also each practice can have many sets. And each set can have exactly one practice. But (and now comes the important part) a practice can have different numbers of sets in different workouts.

So a set relates to a practice and a workout, or?

I don't know how i have to design my erd. Can you please help me?