#include <bits/stdc++.h>
using namespace std;
int main() {
  long int n;
  cin >> n;
  long int h[n];
  long long int ans = 0;
  for (int i = 0; i < n; i++) cin >> h[i];
  if (n == 1)
    cout << h[0] + 1 << endl;
  else {
    for (int i = 0; i < n; i++) {
      if (i == 0 && h[i + 1] >= h[i])
        ans += (h[i] + 1);
      else if (i == 0 && h[i + 1] < h[i])
        ans += h[i] + 1 + h[i] - h[i + 1];
      else if (i == n - 1) {
        if (h[i - 1] <= h[i])
          ans += (h[i] - h[i - 1]) + 1;
        else
          ans += 1;
      } else {
        if (h[i + 1] >= h[i] && h[i - 1] <= h[i])
          ans += (h[i] - h[i - 1]) + 1;
        else if (h[i + 1] <= h[i] && h[i - 1] <= h[i])
          ans += h[i] - h[i - 1] + (h[i] - h[i + 1]) + 1;
        else if (h[i + 1] >= h[i] && h[i - 1] >= h[i])
          ans += 1;
        else
          ans += h[i] - h[i + 1] + 1;
      }
      ans++;
    }
    cout << ans - 1 << endl;
  }
  return 0;
}
