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.

Examples

Input

3

Output

6

Input

10

Output

10

Input

999999999

Output

1999999998

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