Scanf.scanf "%d %d %d %d" (fun a b c d ->
  let rec f a c =
    let c = c - b in
    if c <= 0 then "Yes"
    else g a c
  and g a c =
    let a = a - d in
    if a <= 0 then "No"
    else f a c
  in print_endline (f a c)
)
