1. s : DSet
2. a : MSet{s}
⊢ ||a|| = ||a|| ∈ ℤ
{ ((msetD 2) THENA Auto) }
2. as : |s| List
3. bs : |s| List
4. as ≡(|s|) bs
⊢ ||as|| = ||bs|| ∈ ℤ