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 max = 0;
		int[] line = new int[n - 1];

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

		max += line[0] + line[line.length - 1];

		for (int i = 0; i < n - 2; i++) {
			max += Math.min(line[i], line[i + 1]);
		}

		System.out.println(max);

	}
}
/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