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 JavaScript (Node.js 12.16.1) (judge verdict: Accepted)

const main = (arg) => {
  const lines = arg.trim().split('\n');
  const N = Number.parseInt(lines[0]);
  console.log(N % 2 == 0 ? N : 2 * N);
};
main(require('fs').readFileSync('/dev/stdin', 'utf8'));