import java.util.*;

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 count = b[0];
	for (int i=0; i<n-2; i++)
	    count += Math.min(b[i],b[i+1]);
	count += b[n-2];
	System.out.print(count);
    }
}

/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