import java.util.Scanner;

public 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();
        }

        long sum = b[0];

        for(int i = 1; i < n-1; i++) {
        	sum += (b[i-1] < b[i]) ? b[i-1] : b[i];
        }

        sum += b[n-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