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)

#include <iostream>
#include <string>
#include <algorithm>
#include <set>
#include <numeric>
#include <cmath>
#define rep(i, n) for(int i = 0; i < (int)(n); i++)
#define FOR(i, k, n) for(int i = (k); i < (int)(n); i++)
using namespace std;
using ll = long long;

int main(){
    int N, cnt = 0, ans = 0;
    cin >> N;
    if(N % 2 == 0){
        cout << N << endl;
    }else{
        cout << N * 2 << endl;
    }
    return 0;
}