import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int[] b = new int[n-1];
        for(int i=0;i<n-1;i++){
            b[i] = Integer.parseInt(sc.next());
        }
        int sum = b[0];
        for(int i=1;i<n-1;i++){
            sum+=Math.min(b[i-1],b[i]);
        }
        sum+=b[n-2];
        System.out.println(sum);
        sc.close();
    }
}
/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