#include <bits/stdc++.h>
using namespace std;
int main() {
  vector<int> heightOfTree;
  int numberOfTree;
  scanf("%d", &numberOfTree);
  for (int i = 0; i < numberOfTree; ++i) {
    int height;
    scanf("%d", &height);
    heightOfTree.push_back(height);
  }
  int sum = 0;
  int currentHeight = 0;
  for (int i = 0; i < numberOfTree; i++) {
    if (i == numberOfTree - 1) {
      sum += (heightOfTree[i] - currentHeight) + 1;
    } else if (i == 0) {
      sum += heightOfTree[i] + 1;
      if (numberOfTree > 1) {
        currentHeight = min(heightOfTree[i], heightOfTree[i + 1]);
        if (currentHeight < heightOfTree[i]) {
          sum += heightOfTree[i] - currentHeight;
        }
        sum += 1;
      }
    } else {
      sum += (heightOfTree[i] - currentHeight) + 2;
      currentHeight = min(heightOfTree[i], heightOfTree[i + 1]);
      if (currentHeight < heightOfTree[i]) {
        sum += heightOfTree[i] - currentHeight;
      }
    }
  }
  printf("%d\n", sum);
  return 0;
}
