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)

use std::io;

fn abc(n:i32) -> i32 {
    if n % 2 ==0 {
        return n
    }
    else {
        return n*2
    }
}

fn main() {
    //test
    /*
    assert_eq!(abc(3), 6);
    assert_eq!(abc(10), 10);
    assert_eq!(abc(999999999), 1999999998);
    */
    let stdin = io::stdin();
    let mut line = String::new();
    stdin.read_line(&mut line).ok();
    let txt:Vec<_> = line.trim().split(' ').collect();
    let n:i32 = txt[0].parse().unwrap();


    let result = abc(n);
    println!("{}", result);
}