Score : 100 points

Problem Statement

You are given a positive integer N. Find the minimum positive integer divisible by both 2 and N.

Constraints

  • 1 \leq N \leq 10^9
  • All values in input are integers.

Input

Input is given from Standard Input in the following format:

N

Output

Print the minimum positive integer divisible by both 2 and N.

Sample Input 1

3

Sample Output 1

6

6 is divisible by both 2 and 3. Also, there is no positive integer less than 6 that is divisible by both 2 and 3. Thus, the answer is 6.

Sample Input 2

10

Sample Output 2

10

Sample Input 3

999999999

Sample Output 3

1999999998