object Main {
  def main(args:Array[String]) = {
    val sc = new java.util.Scanner(System.in)
    val n = sc.nextInt
    val bs = Array.fill(n-1)(sc.nextInt)
    val bs2 = 100001 +: bs :+ 100001
    var result = 0
    for(i <- 1 to bs2.length-1) {
      result = result + Math.min(bs2(i-1), bs2(i))
    }
    println(result)
  }
}
