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.Scanner;
public class Main {
@SuppressWarnings("resource")
public static void main(String[] args) {
	Scanner sc=new Scanner(System.in);
	int N=sc.nextInt();
	int B[]=new int[N-1];
	for(int i=0;i<B.length;i++) {
		B[i]=sc.nextInt();
	}
	int ans=B[0];
	for(int i=1;i<B.length;i++) {
		if(B[i-1]>B[i]) {
			ans+=B[i];
		}else {
			ans+=B[i-1];
		}
	}
	ans+=B[N-2];
	System.out.println(ans);

}
}
