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

int main(){
  int N; cin >> N;
  int B[200];
  for (int i = 1; i < N; i++) cin >> B[i];
  int ans = B[1] +B[N-1];
  for (int i = 1; i < N-1; i++) {
    ans += min(B[i],B[i+1]);
  }
  cout << ans << endl;
}
