There is an integer sequence A of length N whose values are unknown.

Given is an integer sequence B of length N-1 which is known to satisfy the following:

B_i \geq \max(A_i, A_{i+1})

Find the maximum possible sum of the elements of A.

Constraints

* All values in input are integers.
* 2 \leq N \leq 100
* 0 \leq B_i \leq 10^5

Input

Input is given from Standard Input in the following format:


N
B_1 B_2 ... B_{N-1}


Output

Print the maximum possible sum of the elements of A.

Examples

Input

3
2 5


Output

9


Input

2
3


Output

6


Input

6
0 153 10 10 23


Output

53
import java.util.ArrayList;
import java.util.List;
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());
		List<Integer> list = new ArrayList<Integer>();
		for(int i = 0; i < N - 1; i++) {
			list.add(Integer.parseInt(sc.next()));
		}
		sc.close();

		int ans = list.get(0);
		for(int i = 1; i < list.size(); i++) {
			ans += Math.min(list.get(i - 1), list.get(i));
		}
		ans += list.get(N - 2);

		System.out.println(ans);
	}

}