refine' .inr ∘ .inr $ lenOne_complete _ _
case zero.zero.zero
stmt : Variable → Variable → ℕ → LoopProgram
h_stmt : stmt = add ∨ stmt = sub
⊢ stmt { index := Nat.zero } { index := Nat.zero } Nat.zero ∈
      Finset.fold (fun a b => a ∪ b) ∅ extendLenOne (ofLen (Nat.zero + Nat.zero + Nat.zero)) ∨
    stmt { index := Nat.zero } { index := Nat.zero } Nat.zero ∈
        Finset.fold (fun x x_1 => x ∪ x_1) ∅
          (fun x =>
            Finset.image (fun x => concat x.1 x.2)
              (Finset.product (ofLen ↑x) (ofLen (Nat.zero + Nat.zero + Nat.zero - ↑x))))
          (Finset.attach (Finset.range (Nat.zero + Nat.zero + Nat.zero))) ∨
      stmt { index := Nat.zero } { index := Nat.zero } Nat.zero ∈ baseProgram (Nat.zero + Nat.zero + Nat.zero + 1)
case zero.zero.zero
stmt : Variable → Variable → ℕ → LoopProgram
h_stmt : stmt = add ∨ stmt = sub
⊢ len (stmt { index := Nat.zero } { index := Nat.zero } Nat.zero) = 1