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.Linq;
using System.Collections.Generic;
using static System.Console;
using static System.Math;
 
public class Hello{
    public static void Main(){
/*        string[] input = ReadLine().Split(' ');
        int n = int.Parse(input[0]);
        int m = int.Parse(input[1]);
//        int a = int.Parse(input[2]);
//        int b = int.Parse(input[3]);*/
//        string temp = ReadLine();
        int a = int.Parse(ReadLine());
//        int b = int.Parse(ReadLine());
//        int c = int.Parse(ReadLine());
//        int d = int.Parse(ReadLine());
//        string a = ReadLine();
//        string b = ReadLine();
//        string c = ReadLine();
        if(a%2==0){
            WriteLine(a);
        }else{
            WriteLine(a*2);
        }
    }
}