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<iostream>
#include<algorithm>
using namespace std;
int main () {
  int n;cin>>n;
  long long int b[n-1],sum=0;
  for (int i=0;i<n-1;i++) cin>>b[i];
  for (int j=0;j<n-2;j++) {
    sum+=min(b[j],b[j+1]);}
  sum+=b[0];sum+=b[n-2];
  cout<<sum<<endl;
}