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];

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

        int sol = 0;

        for (int i = 0; i < N - 2; i++) {
            sol += Math.min(B[i], B[i + 1]);
        }

        sol += B[0] + B[N - 2];

        System.out.println(sol);
    }
}

/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