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
/*package whatever //do not write package name here */

import java.util.*;

public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int s = 0;
		int[] b = new int[n - 1];
		for(int i = 0;i < n - 1;i++)
		{
		    b[i] = sc.nextInt();
		    if(i == 0)
		    s += b[0];
		    if(i > 0)
		    {
		        if(b[i] < b[i - 1])
		        b[i - 1] = b[i];
		    }
		}
		for(int i = 0;i < n - 1;i++)
		s += b[i];
		System.out.println(s);
	}
}