let a : ℕ := 10, b : ℕ := 10, c : ℕ := 10 in f a b (f a 10 c) : ℕ
let a : ℕ := 10,
    b : ℕ := let c : ℕ := 10 in f a c (f a a (f 10 a c)),
    d : ℕ := 10,
    e : ℕ := f (f 10 10 d) (f d 10 10) a
in f a b (f e d 10) :
  ℕ