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


fun intString n =
    if 0 <= n
    then Int.toString n
    else "-" ^ Int.toString (abs n)


val () =
    let
        val n = readInt ()
        val a_s = List.tabulate (n, fn _ => readInt ())
        val v = readInt ()

        val ans =
            (List.foldl
                (fn (x, acc) =>
                    x + acc)
                0
                a_s) - v
    in
        print (intString ans ^ "\n")
    end