let n = stdin.ReadLine() |> float

let rate = 1.08

let ans =
  [ let mutable x = n / rate |> ceil
    while x < (n + 1.) / rate do
      yield x |> int
      x <- x + 1. ]
  |> (fun l ->
        match l with
        | [] -> ":("
        | x :: _ -> sprintf "%d" x)

ans |> stdout.WriteLine