import java.util.*;

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

        int n = sc.nextInt();
        List<Integer> bList = new ArrayList<>();
        for (int i = 0; i < n - 1; i++) {
            bList.add(sc.nextInt());
        }

        int sum = 0;

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

        sum += bList.get(0) + bList.get(n-2);
        System.out.println(sum);
    }
}
/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