#include <bits/stdc++.h>
using namespace std;
const int maxn = 100005;
int n;
int h[maxn];
int main() {
  scanf("%d", &n);
  for (int i = 0; i < n; i++) scanf("%d", &h[i]);
  long long ans = h[0] + 1;
  for (int i = 1; i < n; i++) {
    ans++;
    ans += abs(h[i] - h[i - 1]);
    ans++;
  }
  cout << ans << endl;
}
