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: Accepted)

// -> limitless <- //
#include <bits/stdc++.h>
#define IO ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0);
#define PB push_back
#define MP make_pair
using namespace std;
typedef  long long ll;
    ll gcd(ll a, ll b){
    if(b == 0)return a;
    gcd(b,a%b);
    }
int main()
{
  ll n;
  cin >> n;
  cout << ((n*2)/gcd(n,2)*1ll)<<endl;
	return 0;
}