let minDivsor = function
    | 3L -> Some(3L)
    | 4L -> Some(4L)
    | n  ->
        seq{3L..n}
        |> Seq.takeWhile(fun x -> x*x<=n)
        |> Seq.where(fun x -> n%x=0L)
        |> Seq.tryHead

let n = stdin.ReadLine() |> int64

n
|> minDivsor
|> function
    | Some(x) -> x
    | None    ->
        match n%2L with
        | 0L -> n/2L
        | _  -> n
|> printfn "%i"