import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int answer = 0;
		//int[] a = new int[n];
		int[] b = new int[n - 1];

		for (int i = 0; i < n - 1; i++) {
			b[i] = sc.nextInt();
		}
		answer += b[n - 2];
		for (int i = n - 2; i > 0; i--) {
			answer += Math.min(b[i - 1], b[i]);
		}

		answer += b[0];
		System.out.println(answer);
	}
}

/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