Problem:
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

Solution in Python (2.7.6) (judge verdict: Accepted)

def gcm(i, j):
	k = lcm(i, j)
	return min(i, j) * max(i, j) / k
def lcm(i, j):
	if j > i:
		return lcm(j, i)
	if i % j == 0:
		return j
	k = i % j
	return lcm(j, k)

N = input()
print gcm(2, N)