let N = stdin.ReadLine() |> int
if N % 2 = 0 then N
else
    Seq.initInfinite ((+)1 >> (*)2)
    |> Seq.map (fun n -> n*n)
    |> Seq.filter (fun n -> N-100 <= n && n <= N+100)
    |> Seq.head
|> printfn "%d"