There are ~N~ people in Mr. DeMello's car (including himself in the driver seat) with ~2~ seats in each row. How many people are not adjacent to Mr. DeMello? (Assume that everyone sits as close to Mr. DeMello as possible, and adjacent means either vertically or horizontally at most ~1~ seat away.)

Input Specification

The first line will contain ~N~ ~(0 \le N \le 2^{31})~, the number of people in Mr. DeMello's car.

Output Specification

Output the number of people not adjacent to Mr. DeMello.

Sample Input

15

Sample Output

12