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>
#include <stdlib.h>

unsigned int calculate_solution (unsigned int target)
{
	if (target % 2U == 0U) { return target;      }
	else                   { return target * 2U; }
}

int main (void)
{
	// variables for `main`
	unsigned int N;
	int          retval_scanf;

	// STEP.01
	// read out the given data
	retval_scanf = scanf("%d", &N);

	// STEP.02
	// calcualte & output the points
	printf("%d\n", calculate_solution(N));

	// STEP.END
	return EXIT_SUCCESS;
}