#include <bits/stdc++.h>
using namespace std;

int main() {
  int N;
  cin >> N;
  vector<int> A(N-1);
  for (int &e : A) cin >> e;
  int sum = A[0] + A[N-2];
  for (int i = 0; i < N-2; i++) {
    sum += min(A[i], A[i+1]);
  }
  cout << sum << endl;
}