#include <bits/stdc++.h>
using namespace std;
const int N = 1e6 + 5;
void solve() {
  int n;
  cin >> n;
  vector<int> v(n);
  for (int i = 0; i < n; i++) {
    cin >> v[i];
  }
  int pos = 0;
  int cnt = 0;
  for (int i = 0; i < n - 1; i++) {
    while (pos != v[i]) {
      pos++;
      cnt++;
    }
    cnt++;
    while (pos > v[i + 1]) {
      pos--;
      cnt++;
    }
    while (pos < v[i + 1]) {
      pos++;
      cnt++;
    }
    cnt++;
  }
  while (pos < v[n - 1]) {
    pos++;
    cnt++;
  }
  cnt++;
  cout << cnt;
}
int32_t main() {
  ios::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int t = 1;
  while (t--) {
    solve();
  }
  return 0;
}
