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 (Clang 3.8.0) (judge verdict: Accepted)

#include <iostream>
#include <cstdio>
#include <vector>
#include <math.h>

using namespace std;

typedef long long int ll;
typedef long double ld;

#define rep(i,n) for(int i = 0; i < (n); ++i)
#define vsort(a) sort(a.begin(), a.end())
#define rev(a) reverse(a.begin(), a.end())

const int MOD = 1000000007;
const int INF = INT_MAX;


int main(){

    ll n;
    cin >> n;

    if (n%2 == 0) cout << n << endl;
    else cout << 2*n << endl;
}





//              g++ -std=c++1z