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 9.2.1) (judge verdict: Accepted)

#include <math.h>
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef vector<int> vint;
#define rep(i,n) for (int i = 0; i < (int)(n); ++i)
#define rrep(i,j,n) for(int i = (int)(j); i < (int)(n); i++)
#define mrep(i,n) for (int i = (int)(n-1); i > 0; i--)
#define be(v) (v).begin(), (v).end()
#define scout cout << fixed << setprecision(20)
ll INF = 1LL << 60;
ll mod = 1e9 + 7;
ll MAX=1e18;

int main() {
	int n; cin >> n;
	if(n%2==0) cout << n << endl;
	else cout << n*2 << endl;
}