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 Kotlin (1.0.0) (judge verdict: Accepted)

import java.util.*

fun main(args: Array<String>) {
    multipleOf2AndN()
}

private const val TWO = 2L

fun multipleOf2AndN() {
    val n = Scanner(System.`in`).nextLong()
    val result = n * TWO / gcd(n, TWO)

    println(result)
}

private tailrec fun gcd(m: Long, n: Long): Long {
    if (m < n) return gcd(n, m)
    if (n.toInt() == 0) return m
    return gcd(n, m % n)
}