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# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;

namespace A
{
    class Program
    {
        public static int Gcd(int m, int n) {
            int temp;
            while (m % n != 0) {
                temp = n;
                n = m % n;
                m = temp;
            }
            return n;
        }

        static void Main(string[] args) {
            int N = int.Parse(Console.ReadLine());

            if (N % 2 == 0) Console.WriteLine("N");
            else Console.WriteLine((2 * N / Gcd(2, N)));
        }
    }
}