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
#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  int b1,b2;
  cin >> b1;
  int sum = b1;
  for(int i = 0;i < n - 2;i++) {
    cin >> b2;
    sum += min(b1,b2);
    b1 = b2;
  }
  sum += b1;
  cout << sum << endl;
}