(motive : Nat.Linear.Expr → Sort u_1) →
  (x : Nat.Linear.Expr) →
    ((k : ℕ) → motive (Nat.Linear.Expr.num k)) →
      ((i : Nat.Linear.Var) → motive (Nat.Linear.Expr.var i)) →
        ((a b : Nat.Linear.Expr) → motive (a.add b)) →
          ((k : ℕ) → (a : Nat.Linear.Expr) → motive (Nat.Linear.Expr.mulL k a)) →
            ((a : Nat.Linear.Expr) → (k : ℕ) → motive (a.mulR k)) → motive x