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 JavaScript (node.js v5.12) (judge verdict: Time Limit Exceeded)

function main(input){
	var x = 2, y = Number(input), z, a = x * y;
	if (x < y) {
		t = x;
		x = y;
		y = t;
	}

	z = x % y;
	for (;;) {
		x = y;
		y = z;
		z = x % y;
		if (z === 0) break;
	}

	console.log(a / y);
}
     
main(require("fs").readFileSync("/dev/stdin", "utf8"));