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: Runtime Error)

using System;

namespace B___Maximum_Difference
{
    class Program
    {
        static void Main(string[] args)
        {
            var n =int.Parse( Console.ReadLine());
            var input = Console.ReadLine().Split(' ');
            var a = new int[n];
            var b = 0;
            for (var i = 0; i < n; i++)
            {
                a[i] = int.Parse(input[i]);
            }
            for(var i=0; i<n-1; i++)
            {
                for(var j=1; j<n; j++)
                {
                   if(b< Math.Abs(a[i]-a[j]))
                    {
                        b = Math.Abs(a[i] -a[j]);
                    }
                }
            }
            Console.WriteLine(b);
           
        }
    }
}