fun readStr () =
    valOf (TextIO.inputLine TextIO.stdIn)

val () =
    let
        val s = readStr ()
        val sWithoutCR = String.substring(s, 0, String.size s - 1)
        val ans =
            String.implode
                (
                  List.rev
                      (
                        #2 (List.foldl
                                (fn (c, (i, l)) =>
                                    (i + 1, Char.chr ((Char.ord c - Char.ord #"A" - i) mod 26 + Char.ord #"A") :: l))
                                (1, [])
                                (String.explode sWithoutCR))
                      )
                )
    in
        print (ans ^ "\n")  
    end