let a,b,c,d = Scanf.scanf "%d %d %d %d\n" @@ fun a b c d -> a, b, c, d
let rec f a b c d t =
  if a <= 0 then false else if c <= 0 then true
  else if t then f a b (c-b) d false else f (a-d) b c d true
let ans = if (f a b c d true) then "Yes" else "No"
let () = print_endline ans