import java.util.ArrayList;
import java.util.Scanner;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

public class Main {

  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);

    int n = sc.nextInt();
    ArrayList<Integer> as = new ArrayList<>();
    ArrayList<Integer> bs = new ArrayList<>();

    for (int i = 0; i < n-1; i++) {
      bs.add(sc.nextInt());
    }

    int ans = bs.get(0) + bs.get(n-2);

    for (int i = 0; i < n-2; i++) {
      ans += Math.min(bs.get(i), bs.get(i+1));
    }

    System.out.println(ans);
  }
}

/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz