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 Go (1.6) (judge verdict: Accepted)

package main

import "fmt"

func main() {
	var N int64
	fmt.Scan(&N)
	for Ns := N; ; Ns += N {
		if Ns%2 == 0 && Ns%N == 0 {
			fmt.Println(Ns)
			break
		}
	}
}