Problem Description

JOI is taking a walk on a straight road.

JOI alternates between the following actions in the order Action A → Action B → Action A → …:

• Action A: Move $3\text{ m}$ forward.
• Action B: Move $2\text{ m}$ backward.

When he has performed Action A and Action B a total of $X$ times, how many $\text{m}$ forward from the starting position has he moved?

Constraints

• $1 \le X \le 100$.
• $X$ is an integer.

Input

The input is given in the following format:
$X$

Output

Output the distance in $\text{m}$ moved forward from the starting position, omitting the unit ($\text{m}$).

Do not output anything other than the answer. (Do not output prompt messages for input, etc.)

For the answer format, you may also refer to the practice problems and their sample solutions.

Sample Input 1

3

Sample Output 1

4

• Move $3\text{ m}$ forward.
• Move $2\text{ m}$ backward.
• Move $3\text{ m}$ forward.

He performs a total of $3$ actions as above, so he has moved $4 (= 3 - 2 + 3)\text{ m}$ forward from the starting position. Therefore, output $4$.

Sample Input 2

6

Sample Output 2

3

• Move $3\text{ m}$ forward.
• Move $2\text{ m}$ backward.
• Move $3\text{ m}$ forward.
• Move $2\text{ m}$ backward.
• Move $3\text{ m}$ forward.
• Move $2\text{ m}$ backward.

He performs a total of $6$ actions as above, so he has moved $3 (= 3 - 2 + 3 - 2 + 3 - 2)\text{ m}$ forward from the starting position. Therefore, output $3$.

Sample Input 3

1

Sample Output 3

3

• Move $3\text{ m}$ forward.

He performs a total of $1$ action as above, so he has moved $3\text{ m}$ forward from the starting position. Therefore, output $3$.

Sample Input 4

37

Sample Output 4

21

Since he has moved $21\text{ m}$ forward from the starting position, output $21$.

Sample Input 5

100

Sample Output 5

50

Since he has moved $50\text{ m}$ forward from the starting position, output $50$.