import java.util.*;

public class Main
{
	public static void main(String args[])
	{
		Scanner scan = new Scanner(System.in);
		int n = scan.nextInt();
		int[] b = new int[n-1];
		for(int i=0;i<n-1;i++)
		{
			b[i]=scan.nextInt();
		}
		solve(n,b);
		scan.close();	
	}
	
	private static void solve(int n,int b[])
	{
		int a=b[0];
		for (int i = 0; i < n - 2; i++)
			if (b[i] <= b[i + 1])
				a += b[i];
			else
				a += b[i + 1];
		a += b[n - 2];
		System.out.println(a);
	}
}
/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