import java.util.*;
class Main{
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n];
        int[] b = new int[n-1];
        for(int i = 0;i<n-1;i++){
            b[i] = sc.nextInt();
        }
        for(int i =0;i<n;i++){
            if(i==0){
                a[i]=b[i];
            } else if(i==n-1){
                a[i]=b[i-1];
            }else {
                a[i]=Math.min(b[i],b[i-1]);
            }
        }
        int sum = 0;
        for(int i =0;i<n;i++){
            sum += a[i];
        }
        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