(* O(n) *)
let find_btw f from n =
  let rec find i = if i >= n || f i then i else find (i + 1) in find from

(* O(|a_s|^2) *)
let solve a_s k =
  let n = Array.length a_s in
  if n = find_btw
    (fun i -> n > find_btw (fun j -> a_s.(j) - a_s.(i) > k) (i + 1) n)
    0
    n then "Yay!" else ":("

let read_int_array n = Array.init n (fun _ -> read_int ())

let _ =
  match read_int_array 6 with
  | [|a; b; c; d; e; k|] -> solve [|a; b; c; d; e|] k |> print_endline
  | _ -> ()