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 Pascal (FPC 2.6.2) (judge verdict: Time Limit Exceeded)

var
  n:integer;
  answer:integer;
begin
  readln(n);
  answer := n;
  while (answer mod n > 0) or (answer mod 2 > 0) do answer := answer + 1;
  write(answer);
end.