object Main {
  def main(args: Array[String]): Unit = {
    val sc = new java.util.Scanner(System.in)
    val n = sc.nextInt
    val b = List.fill(n - 1)(sc.nextInt)
    sc.close

    val ans = (1 until n - 1).foldLeft(b.head + b.last)((acc, cur) => {
      acc + Math.min(b(cur - 1), b(cur))
    })

    println(ans)
  }
}