import java.util.Scanner;

/**
 * Created by Sohail on 9/7/2019.
 */

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int x = sc.nextInt();
        long[] b = new long[x];
        for(int i = 0; i < x-1; i++){
            b[i] = sc.nextInt();
        }
        long tot = b[0];
        for(int i = 0; i < x-1; i++){
            tot += Math.min(b[i],b[i+1]);
        }
        System.out.println(tot+b[x-2]);
    }
}


/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