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];
		long sumA = 0;

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

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

		System.out.println(sumA);
	}

}
/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