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

int main() {
  int A;
  cin >> A;
  int B;
  cin >> B;
  int C;
  int D = B;
  for(int i = 0;i < A - 2;i++){
    cin >> C;
    D = D + min(B, C);
    B = C;
  }
  cout << B + D << endl;
}