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


val () =
    let
        val a = readInt ()
        val b = readInt ()

        val ans = if a < b then (b - 1) - 1
                  else          (* a > b *)
                      (2 * 1000000000 - b) - 1
    in
        print (Int.toString ans ^ "\n")
    end