rcases hlit with ⟨clause, ⟨hclause1, hclause2⟩⟩
maxLit : Nat
c : CNF Nat
h : c.maxLiteral = some maxLit
lit : Nat
hlit : ∃ c_1, c_1 ∈ c ∧ Clause.mem lit c_1
⊢ lit ≤ maxLit
case intro.intro
maxLit : Nat
c : CNF Nat
h : c.maxLiteral = some maxLit
lit : Nat
clause : Clause Nat
hclause1 : clause ∈ c
hclause2 : Clause.mem lit clause
⊢ lit ≤ maxLit