# 4 Key Keyboard

hard

1. Imagine you have a special keyboard with the following keys - Key 1 : Print 'X' on the screen. key 2 : Select screen. Key 3 : Copy selection to buffer. Key 4 : Print buffer on screen appending to what has already been printed. 2. You are given a number N, which represents the number of times the keyboard is pressed. 3. You have to find the maximum number of 'X' that can be produced by pressing the N number of keys.

## Constraints

1 <= N <= 100

## Format

### Input

A number N

### Output

Check the sample output and question video.

## Example

Sample Input

3

### Sample Output

3