import java.util.*;
public class Main {
 public static void main(String[] args){
	Scanner sc = new Scanner(System.in);
	int n=sc.nextInt(); long r=0;
	LinkedList<Integer> stok = new LinkedList<Integer>();
	stok.add(Integer.MAX_VALUE);
    for(int i=1;i<n;i++){
		stok.add(sc.nextInt());
		r+=Math.min(stok.get(0),stok.get(1));
		stok.remove(0);
	}
	System.out.println(r+stok.get(0));
 }
}
/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