import java.util.Scanner;

public class Main {

    public static void main(String[] args) {

        Scanner sc = new Scanner(System.in);
        int N = Integer.parseInt(sc.next());
        int[] Bi = new int[N-1];
        for (int i = 0; i < N-1; i++) {

            Bi[i] = Integer.parseInt(sc.next());
        }
        sc.close();

        //最大値は10^5*101なのでintで十分かと
        int ans = 0;

        ans += Bi[0] + Bi[N-2];

        for (int i = 1; i < N-1; i++) {

            ans += Math.min(Bi[i-1], Bi[i]);
        }

        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