import java.util.*;

class Main {
    public static void main(String[] args) throws java.lang.Exception {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] b = new int[n - 1];
        for (int i = 0; i < n - 1; i++) {
            b[i] = sc.nextInt();
        }
        sc.close();
        int a = b[0];
        for (int i = 0; i < n - 2; i++) {
            a += Math.min(b[i], b[i + 1]);
        }
        a += b[n - 2];
        System.out.println(a);
    }
}

/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