import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.nextLine());
        int[] b = new int[n];
        String line = sc.nextLine();
        String[] line1 = line.split(" ");
        for(int i = 0; i < n - 1; i++) b[i] = Integer.parseInt(line1[i]);
        int count = 0;
        if(n == 2)  count += b[0] * 2;
        else{
            if(b[0] <= b[1]) count += b[0] * 2;
            else    count += b[0] + b[1];
            for(int i = 1; i < n - 2; i++){
                if(b[i] > b[i + 1]) count += b[i + 1];
                else count += b[i];
            }
            count += b[b.length - 2];
        }
        System.out.println(count);
    }
}
/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