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 read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

//fn read_vec<T: std::str::FromStr>() -> Vec<T> {
//    read::<String>().split_whitespace()
//        .map(|e| e.parse().ok().unwrap()).collect()
//}

//fn read_vec2<T: std::str::FromStr>(n: u32) -> Vec<Vec<T>> {
//    (0..n).map(|_| read_vec()).collect()
//}

fn main() {
    let n:u32 = read();
    let ans =
        if n%2==0 {n} else {n*2};
    println!("{}", ans)
}