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[] a = new int[n];
        a[0] = b[0];
        a[n-1] = b[n-2];
        for(int i = 1; i < n-1; i++){
            a[i] = Math.min(b[i-1], b[i]);
        }
        
        int ans = 0;
        for(int i = 0; i < n; i++){
            ans += a[i];
        }
        
        System.out.println(ans);
    }
}
/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