import java.util.*;
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();
    }
    if(n==2){
      System.out.println(b[0]*2);
      System.exit(0);
    }
    int sum=b[n-2]+b[0];
    for(int i=n-2;i>=1;i--){
      sum+=Math.min(b[i],b[i-1]);
    }
    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