let minDivsor n =
    seq{3L..n|>float|>sqrt|>int64}
    |> 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"