Problem Statement

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

Input

Input is given from Standard Input in the following format:
N

Output

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

Constraints

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

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

见题面 Input 部分

见题面 Output 部分