import java.util.Scanner;

public class Main {

  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);
    int n = sc.nextInt();
    int[] b = new int[n - 1];
    int ans = 0;

    for (int i = 0; i < (n - 1); i++) {
      b[i] = sc.nextInt();
    }

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

    ans += b[0];
    ans += b[n - 2];

    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