Squirrel Liss loves nuts. There are n trees (numbered 1 to n from west to east) along a street and there is a delicious nut on the top of each tree. The height of the tree i is hi. Liss wants to eat all nuts.

Now Liss is on the root of the tree with the number 1. In one second Liss can perform one of the following actions:

  * Walk up or down one unit on a tree. 
  * Eat a nut on the top of the current tree. 
  * Jump to the next tree. In this action the height of Liss doesn't change. More formally, when Liss is at height h of the tree i (1 ≤ i ≤ n - 1), she jumps to height h of the tree i + 1. This action can't be performed if h > hi + 1. 



Compute the minimal time (in seconds) required to eat all nuts.

Input

The first line contains an integer n (1 ≤ n ≤ 105) — the number of trees.

Next n lines contains the height of trees: i-th line contains an integer hi (1 ≤ hi ≤ 104) — the height of the tree with the number i.

Output

Print a single integer — the minimal time required to eat all nuts in seconds.

Examples

Input

2
1
2


Output

5


Input

5
2
1
2
1
1


Output

14
import java.io.*;
import java.math.*;
import java.util.*;
 
 
 
 
 
public class A {
 
    static MyScanner in = new MyScanner();
    static   PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
    static BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    static StringTokenizer st;
    static long H,W;
    static BitSet bs;
    static long mod = 1000000007;
      // All possible moves of a knight 
    static   int X[] = { 2, 1, -1, -2, -2, -1, 1, 2 }; 
    static int Y[] = { 1, 2, 2, 1, -1, -2, -2, -1 }; 
    public static void main(String args[]) throws IOException {
     int n = in.nextInt();
     int [] a = new int[n];
     for(int i=0;i<n;i++){
         a[i] = in.nextInt();
     }
     int action = a[0]+1;
     for(int i=1;i<n;i++){
        int dif = Math.abs(a[i]-a[i-1]);
        action+=dif;
        action+=2;

     }
     out.println(action);
     out.flush();
    }
    static boolean isVowel(char c){
        if(c=='a'||c=='e'||c=='i'||c=='o'||c=='u'||c=='y'){
            return true;
        }
        return false ;
    }
    static class IP implements Comparable<IP>{
        public int first,second;
        IP(int first, int second){
            this.first = first;
            this.second = second;
        }
        public int compareTo(IP ip){
            if(first==ip.first)
                return second-ip.second;
            return first-ip.first;    
        }
 
    }
        
       static long gcd(long a, long b){
        return b!=0?gcd(b, a%b):a;
    }
 
        static boolean isEven(long a) {
            return (a&1)==0;
        }
    
    public static class MyScanner {
        BufferedReader br;
        StringTokenizer st;
   
        public MyScanner() {
           br = new BufferedReader(new InputStreamReader(System.in));
        }
   
        String next() {
            while (st == null || !st.hasMoreElements()) {
                try {
                    st = new StringTokenizer(br.readLine());
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            return st.nextToken();
        }
   
        int nextInt() {
            return Integer.parseInt(next());
        }
   
        long nextLong() {
            return Long.parseLong(next());
        }
   
        double nextDouble() {
            return Double.parseDouble(next());
        }
   
        String nextLine(){
            String str = "";
        try {
           str = br.readLine();
        } catch (IOException e) {
           e.printStackTrace();
        }
        return str;
        }
  
     }
}