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 Rust (1.15.1) (judge verdict: Accepted)

fn main(){
	let mut s = String::new();
	std::io::stdin().read_line(&mut s).unwrap();
	let n: i64 = s.trim().parse().unwrap();
	let mut x: i64 = n;
	loop {
		if x % 2 == 0 && x % n == 0 {
			println!("{}", x);
			break;
		}
		x *= 2;
	}
}