let getClass m xy =
  let xy' = xy - 1 in
  let isEven = (xy' / m) mod 2 = 0 in
  if isEven then xy' mod m
  else (m - 1) - (xy' mod m)

let () =
  let _, m = read_line () |>
             Str.split (Str.regexp_string " ") |>
             List.map int_of_string |>
             (fun lst -> (List.nth lst 0, List.nth lst 1))
  and x, y = read_line () |>
             Str.split (Str.regexp_string " ") |>
             List.map int_of_string |>
             (fun lst -> (List.nth lst 0, List.nth lst 1))
  in
  let hanako = getClass m x
  and taro = getClass m y
  in
  (hanako = taro) |>
  (function | true -> "YES" | false -> "NO") |>
  print_endline