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
"""
    Author: Sagar Pandey

"""
# ---------------------------------------------------Import Libraries---------------------------------------------------
import sys
import time
import os
from math import sqrt, log, log2, ceil, log10, gcd, floor, pow, sin, cos, tan, pi, inf, factorial
from copy import copy, deepcopy
from sys import exit, stdin, stdout
from collections import Counter, defaultdict, deque
from itertools import permutations
import heapq
from bisect import bisect_left as bl
# If the element is already present in the list,
# the left most position where element has to be inserted is returned.
from bisect import bisect_right as br
from bisect import bisect

# If the element is already present in the list,
# the right most position where element has to be inserted is r

# ---------------------------------------------------Global Variables---------------------------------------------------
# sys.setrecursionlimit(100000000)
mod = 1000000007
# ---------------------------------------------------Helper Functions---------------------------------------------------
iinp = lambda: int(sys.stdin.readline())
inp = lambda: sys.stdin.readline().strip()
strl = lambda: list(inp().strip().split(" "))
intl = lambda: list(map(int, inp().split(" ")))
mint = lambda: map(int, inp().split())
flol = lambda: list(map(float, inp().split(" ")))
flush = lambda: stdout.flush()


def permute(nums):
    def fun(arr, nums, cur, v):
        if len(cur) == len(nums):
            arr.append(cur.copy())
        i = 0
        while i < len(nums):
            if v[i]:
                i += 1
                continue
            else:
                cur.append(nums[i])
                v[i] = 1
                fun(arr, nums, cur, v)
                cur.pop()
                v[i] = 0
                i += 1
            # while i<len(nums) and nums[i]==nums[i-1]:i+=1    # Uncomment for unique permutations
        return arr

    res = []
    nums.sort()
    v = [0] * len(nums)
    return fun(res, nums, [], v)


def subsets(res, index, arr, cur):
    res.append(cur.copy())
    for i in range(index, len(arr)):
        cur.append(arr[i])
        subsets(res, i + 1, arr, cur)
        cur.pop()
    return res


def sieve(N):
    root = int(sqrt(N))
    primes = [1] * (N + 1)
    primes[0], primes[1] = 0, 0
    for i in range(2, root + 1):
        if primes[i]:
            for j in range(i * i, N + 1, i):
                primes[j] = 0
    return primes


def bs(arr, l, r, x):
    if x < arr[0] or x > arr[len(arr) - 1]:
        return -1
    while l <= r:
        mid = l + (r - l) // 2
        if arr[mid] == x:
            return mid
        elif arr[mid] < x:
            l = mid + 1
        else:
            r = mid - 1
    return -1


def isPrime(n):
    if n <= 1: return False
    if n <= 3: return True
    if n % 2 == 0 or n % 3 == 0: return False
    p = int(sqrt(n))
    for i in range(5, p + 1, 6):
        if n % i == 0 or n % (i + 2) == 0:
            return False
    return True


# -------------------------------------------------------Functions------------------------------------------------------
def fun(arr, mid, l):
    n = len(arr)
    if mid < arr[0] or mid < l - arr[-1]:
        return False
    for i in range(n - 1):
        if not arr[i] + mid >= arr[i + 1] - mid:
            return False
    return True


def solve():
    n=iinp()
    arr=[]
    prev=0
    ans=0
    for i in range(n):
        arr.append(iinp())
    # print(arr)
    ans=n+n-1+arr[0]
    # print(ans)
    for i in range(1,n):
        # print(ans)
        if arr[i]<arr[i-1]:
            ans+=arr[i-1]-arr[i]
        else:
            ans+=arr[i]-arr[i-1]
    print(ans)



# -------------------------------------------------------Main Code------------------------------------------------------
start_time = time.time()
# for _ in range(iinp()):
solve()
# print("--- %s seconds ---" % (time.time() - start_time))
