CF265B 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

The first line contains an integer $ n $ ( $ 1

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