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 C (GCC 5.4.1) (judge verdict: Accepted)

#include <stdio.h>

int gcd(int a, int b) {
	return b == 0 ? a : gcd(b, a % b);
}

int lcm(int a, int b) {
	return a * (b / gcd(a, b));
}

int main() {
	int n;

	scanf("%d", &n);
	printf("%d\n", lcm(n, 2));
	return 0;
}