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

        Integer[] a = new Integer[n - 1];
        for (int i = 0; i < n - 2; i++) {
            if (b[i] < b[i+1]) {
                a[i] = b[i];
            } else {
                a[i] = b[i + 1];
            }
        }
        a[a.length - 1] = b[b.length - 1];

        int result = b[0];
        for (int num : a) {
            result+=num;
        }

        System.out.println(result);
    }
}

/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