import java.util.*;
 
public class Main{
	public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    int number = sc.nextInt();
    int[] b = new int[number-1];
    int sum = 0;
      
    for(int i = 0; i < number-1; i++){
    	b[i] = sc.nextInt();
    }
    sum += b[0];
    for(int j = 0; j < number-2; j++){
       if(b[j] >= b[j+1]){
       	sum += b[j+1];
       }else{
       	sum += b[j];
       }
    }
      
    sum += b[number-2];
    System.out.println(sum);
    }
}
/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