let read () = Scanf.scanf "%d " (fun i -> i)
let () =
  let n = read () in
  let rec doit i sum =
    if i = n then sum
    else doit (i + 1) (sum + read ()) in
  let s = doit 0 0 in
  let v = read () in
  Printf.printf "%d\n" (s - v)