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: Accepted)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Contest.cs
{
	class Program
	{
		static void Main(string[] args)
		{
			int n = ReadInt()[0];
			int ans;
			if (n % 2 == 0)
			{
				ans = n;
			}
			else
			{
				ans = n * 2;
			}
			Console.WriteLine(ans);
		}

		static string[] ReadStr()
		{
			return Console.ReadLine().Split(' ').ToArray();

		}

		static int[] ReadInt()
		{
			return Console.ReadLine().Split(' ').Select(x => int.Parse(x)).ToArray();
		}
	}
}