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.*;
public class Main{
    public static void main(String [] args){
        Scanner sc = new Scanner(System.in);
        int N = sc.nextInt();
        int[] A = new int[N];
        int[] B = new int[N-1];
        for(int i = 0; i < N-1; i++)B[i] = sc.nextInt();

        A[0] = B[0];
        for(int i = 1; i < N-1; i++){
            A[i] = Math.min(B[i],B[i-1]);
        }
        A[N-1] = B[N-2];
        int sum = 0;
        for(int i = 0; i < N; i++) sum += A[i];
        System.out.println(sum);
    }
}