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 (Clang 3.8.0) (judge verdict: Runtime Error)

//Atcoder Begineer Contest102
//B - Maximum Difference
//2018/07/01 20:47

#include<stdio.h>
#define MAX 100

int main(void)
{
  int i;
  int N;
  int A[MAX]={};
  int max = 0;
  int min = 100000000;

  scanf("%d",&N);

  for(i=0;i<N;i++){
    scanf("%d",&A[i]);
    if(min>A[i]){
      min = A[i];
    }
    if(max<A[i]){
      max = A[i];
    }
  }

  printf("%d",max-min);

  return 0;
}