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++14 (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <bits/stdc++.h>
using namespace std;

/* メモリ食い過ぎ注意 */
#define int long long

typedef long long ll;

/* define const */
const ll INF = (1ll << 60);
const ll MOD = (ll)1e9 + 7;
/* end defineing */

signed main()
{
    int n;
    cin >> n;

    if (n % 2 == 0)
        cout << n << endl;
    else
    {
        cout << n + 1 << endl;
    }
}