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.IO;
using System.Text;
using System.Text.RegularExpressions;
using System.Diagnostics;
//var input = Console.ReadLine().Split().Select(int.Parse).ToArray();
namespace AtCoderSolve
{
    class Solve
    {
        const int mod = 1000000007;
        static void Main(string[] args)
        {
            //var watch = new Stopwatch();
            var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
            Console.SetOut(sw);

            long N = long.Parse(Console.ReadLine());
            Console.WriteLine(N % 2 == 0 ? N : 2 * N);
            
            
            //watch.Start();

           

            Console.Out.Flush();
            /*watch.Stop();

            Console.WriteLine($"time:{watch.ElapsedMilliseconds} ms"); //Debug Only.
            Console.Out.Flush();*/
        }
    }
    


    public class Calculation
    {
        
    }

    public class Graph
    {

    }
}