let ``No.163 cAPSlOCK``() =
  
  stdin.ReadLine()
  |> Seq.iter (fun c -> 
    match System.Char.IsUpper c with
    | false -> c |> System.Char.ToUpper |> stdout.Write 
    | true  -> c |> System.Char.ToLower |> stdout.Write 
    )
  stdout.WriteLine ""

``No.163 cAPSlOCK``()