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 JavaScript (node.js v5.12) (judge verdict: Accepted)

function Main(input){
	input = input.trim();
  return input % 2 ? input * 2 : input;
}

// If you are interested in the algorithms I used, 
// there is no need to read down from this line.

((b,c,d)=>"undefined"!=typeof require?console.log(Main(require("fs").readFileSync("/dev/stdin","utf8"))):[b=b.split("\n").slice(1,-1).join("\n"),c=function(){try{return Main(b)}catch(f){return f.stack||f.message}}(),d=typeof c,"string"==d||(c=JSON.stringify(c)),$("<form>").append([[10,b],0,[1,d],0,[10,c]].map(f=>$(f?"<textarea>":"<br>",f&&{rows:f[0],cols:40,text:f[1]}))).appendTo("body")])(`
10
`);