fun readInt () =
    valOf (TextIO.scanStream (Int.scan StringCvt.DEC) TextIO.stdIn)


val () =
    let
        val a = Word.fromInt (readInt ())
        val c = Word.fromInt (readInt ())

        val b = Word.xorb (a, c)
    in
        print (Word.toString b ^ "\n")
    end