Problem Statement

Ramadan Kareem! Gargee'an is a celebration that takes place on the 15th night of the Islamic holy month of Ramadan. Children from all around the neighborhood dress in traditional attire and go from door-to-door to receive sweets and nuts from neighbours while singing traditional songs.

Nouf loves this celebration and want to collect as many sweets as she can. Given the number of neighbours N, calculate how many candies can Nouf collect. Assume that each neighbour will give Nouf, exactly 2 candies.

Constraints

N is an integer from 1 to 20 which is the number of neighbours.

Input

Input is in the following format:

N

Output

Print the total amount of candies.

Samples

Sample 1

Sample 2

Sample 3