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 5.4.1) (judge verdict: Time Limit Exceeded)

#include <stdio.h>
#define MAX 9999999999

int main(void)
{
    int mod=2;
    int N;
     
     scanf("%d", &N);
     while(mod <= MAX)
     {
         if ((mod%2 == 0) && (mod%N == 0)){
               printf("%d", mod);
               break;
         }
         mod += 2; //2で割れる==必ず偶数
     }
     return 0;
}