type ABC(stream:System.IO.TextReader) =
  member this.Scan4 f1 f2 f3 f4 = stream.ReadLine().Split() |> (fun a -> (f1 a.[0], f2 a.[1], f3 a.[2], f4 a.[3]))

let util = ABC(stdin)
let W,H,x,y = util.Scan4 float float float float
let area = W * H / 2.0
match W=2.0*x, H=2.0*y with
| true, true -> "1"
| _ -> "0"
|> printfn "%.10f %s" area