Special Keyboard :
Difficulty Level : Medium
Submissions : 623
Asked In :
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Imagine you have a special keyboard with the following keys:
Key 1: Prints $$$A$$$ on screen
Key 2: $$$(Ctrl-A)$$$: Select screen
Key 3: $$$(Ctrl-C)$$$: Copy selection to buffer
Key 4: $$$(Ctrl-V)$$$: Print buffer on screen appending it after what has already been printed.
Find the maximum numbers of $$$A's$$$ that can be produced by pressing keys on the special keyboard $$$N$$$ times.
Input
The first line contains a single integer $$$N$$$.$$$(2\le N \le75).$$$
Output
Your task is to return the maximum number of $$$A's$$$ that can be on the screen after performing $$$N$$$ operations.
Examples
Input
7
Output
9
Input
2
Output
2
