let a, b, c, d = Scanf.sscanf (read_line ()) "%d %d %d %d" @@ fun a b c d -> (a, b, c, d)

let rec loop t a c =
  if t then
    if b >= c then "Yes" else loop false a (c - b)
  else
    if d >= a then "No" else loop true (a - d) c

let () = print_endline @@ loop true a c