A8783 | Roadside Trees (Simplified Edition)

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 $h_{i}$ . 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 $h>h_{i+1}$ .

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

The first line contains an integer $n$ ( $1<=n<=10^{5}$ ) — the number of trees.

Next $n$ lines contains the height of trees: $i$ -th line contains an integer $h_{i}$ ( $1<=h_{i}<=10^{4}$ ) — the height of the tree with the number $i$ .

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