import scala.io.StdIn
object Main extends App {
  val N = StdIn.readLine().toInt
  val B = StdIn.readLine().split(" ").map(_.toInt).toList
  val answer = for {
    i <- 0 to N-2
    a = if (i == 0) B(0) else B(i).min(B(i-1))
  } yield a
  println(answer.sum + B(N-2))
}
