#include <bits/stdc++.h>
using namespace std;
long long MOD = 998244353;
double eps = 1e-12;
void solve() {
  int n;
  cin >> n;
  vector<int> v;
  int temp;
  for (int i = 0; i < n; i++) {
    cin >> temp;
    v.push_back(temp);
  }
  int ans = 0;
  ans = v[0] + 1;
  for (int i = 1; i < n; i++) {
    ans++;
    if (v[i - 1] < v[i]) {
      ans = ans + v[i] - v[i - 1] + 1;
    } else {
      ans = ans + v[i - 1] - v[i] + 1;
    }
  }
  cout << ans << "\n";
}
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int t = 1;
  while (t--) {
    solve();
  }
  return 0;
}
