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;
  vector<int> b(n - 1);
  for (auto &e : b) cin >> e;
  int r = b.front() + b.back();
  for (int i = 0; i + 1 < n - 1; i++) r += min(b[i], b[i + 1]);
  cout << r << endl;
}
