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
from collections import deque, Counter, OrderedDict
from heapq import nsmallest, nlargest
from math import ceil,floor,log,log2,sqrt,gcd,factorial,pow,pi
from bisect import bisect_left,bisect_right

def binNumber(n,size=4):
    return bin(n)[2:].zfill(size)

def iar():
    return list(map(int,input().split()))

def ini():
    return int(input())

def isp():
    return map(int,input().split())

def sti():
    return str(input())

def par(a):
    print(' '.join(list(map(str,a))))

def tdl(outerListSize,innerListSize,defaultValue = 0):
    return [[defaultValue]*innerListSize for i in range(outerListSize)]

def sts(s):
    s = list(s)
    s.sort()
    return ''.join(s)

class pair:
    def __init__(self,f,s):
        self.fi = f
        self.se = s
    def __lt__(self,other):
        return (self.fi,self.se) < (other.fi,other.se)

#  =========     /\       /|    |====/|
#      |        /  \       |    |   / |
#      |       /____\      |    |  /  |
#      |      /      \     |    | /   |
#  ========= /        \  =====  |/====|  
#  code

if __name__ == "__main__":
    n = ini()
    h = []
    cnt = 0
    for i in range(n):
        h.append(ini())
    cnt += h[0] + 2
    for i in range(1,n):
        cnt += (abs(h[i-1] - h[i]) + 2)
    cnt -= 1
    print(cnt)