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: Wrong Answer)

#include<stdio.h>

int abs(int a[], int max,int n,int i,int sum) {
	if ((max - n) + a[i] < i + 1) sum += ((i + 1) - ((max - n) + a[i]));
	else sum += ((a[i] + (max - n)) - (i + 1));
	return sum;
}

int main(void) {
	int  n, a[200000] = { 0 }, i, sum = 0, max;
	scanf("%d", &n);
	scanf("%d", &a[0]);
	max = a[0];
	for (i = 1; i < n; i++) {
		scanf("%d", &a[i]);
		if (max < a[i]) max = a[i];
	}
	for (i = 0; i, n; i++) {
		abs(a, max, n, i, sum);
	}
	printf("%d", sum);
  	return 0;
}