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: Time Limit Exceeded)

#include<bits/stdc++.h>
using namespace std;
#define el '\n'
#define ull unsigned long long
#define ui unsigned int
#define ll long long
#define sf(n) scanf("%d",&n)
#define pf(n) printf("%d",n)
int main()
{
    ll n;
    cin>>n;
    for(ll i=n;;i++)
    {
        if(i%2==0 && i%n==0)
        {
            cout<<i<<el;
            break;
        }
    }
    return 0;
}