import java.util.Scanner

object Main extends App {
  val sc = new Scanner(System.in)

  val n = sc.nextInt

  val al = List.fill(n)(sc.nextInt)
  val bl = List.fill(n)(sc.nextInt)
  val cl = List.fill(n - 1)(sc.nextInt)


  val res = al.foldLeft((0,-10)){case ( (sum, pre), ii) =>
    val i = ii - 1
    val newsum = sum + bl(i) + (if(i == pre + 1) cl(i - 1) else 0)
    (newsum, i)
  }._1

  println(res)

}
