import scala.math.min

object Main extends App {
  
  val sc = new java.util.Scanner(System.in)
  val n = sc.nextInt()
  val b = Array.fill(n-1)(sc.nextInt())
  val initDigit = 100000
  var a = Array.fill(n)(initDigit)
  for (i <- n-1 to 0 by -1) {
    if (i == n-1) {
      a(i) = b(i-1)
    } else if (i == 0) {
      a(i) = b(i)
    } else {
      a(i) = min(b(i), b(i-1))
    }
  }
  println(a.sum)
}