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 C (GCC 5.4.1) (judge verdict: Accepted)

#include <stdio.h>

int main(int argc, char const *argv[]) {
  int N;
  //入力
  scanf("%d", &N );
  //計算
  int answer;
  if ( N%2 == 0) {
    answer = N;
  } else {
    answer = 2*N;
  }
  //出力
  printf("%d\n", answer );
  return 0;
}