#include <bits/stdc++.h>
using namespace std;
int n, a[105], b[105], ans = 0;
int main() {
  cin >> n;
  for (int i = 1; i < n; ++i) cin >> a[i];
  b[1] = a[1], b[2] = a[1];
  for (int i = 2; i < n; ++i) {
    b[i + 1] = a[i];
    b[i] = min(a[i - 1], a[i]);
  }
  for (int i = 1; i <= n; ++i) ans += b[i];
  cout << ans << endl;
  return 0;
}
