import java.util.Scanner

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

  val n = sc.nextInt

  val bv = Vector.fill(n - 1)(sc.nextInt)

  val res = (bv :+ Int.MaxValue).foldLeft((0, Int.MaxValue)){case ((sum, pre), b) =>
    (sum + Math.min(pre, b), b)
  }._1
  
  println(res)
}
