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