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 (GCC 5.4.1) (judge verdict: Accepted)

#include<stdio.h>
int main()
{
	long a=2,b,t,p,s,h;
	scanf("%d",&b);
	s=a*b;
	if(a<b)
	{
		t=b;
	    b=a;
		a=t;
	}
	while(p=a%b,p!=0)
	{
       a=b;
	   b=p;
	}
	h=s/b;
	printf("%d\n",h);
	return 0;
}