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)

struct MyIo{

}

impl MyIo{
    fn readline()->Vec<String>{
        let mut buf = String::new();
        std::io::stdin().read_line(&mut buf).unwrap();
        let ret:Vec<String> = buf.split_whitespace().map(|c|c.to_string()).collect();
        ret
    }
}


fn main() {

    let mut input = MyIo::readline().into_iter();
    let N = input.next().unwrap().parse::<u32>().unwrap();

    if N%2==0{
        println!("{:?}",N);
    }else{
        println!("{:?}",N*2);
    }
}