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 main() {
	int N, a = 2;
	scanf("%d", &N);
	if (N >= 500000000) {
		for (int n = 500000000; n <= 1999999998; n++) {
			if (n % N == 0) {
				printf("%d\n", n);
				if (n % 2 == 0) {
					printf("%d", n);
					return 0;
				}
			}
		}
	}
	for (int n = 1; n <= 1999999998; n++) {
		if (n % N == 0) {
			printf("%d\n", n);
			if (n % 2 == 0) {
				printf("%d", n);
				return 0;
			}
		}
	}
	printf("error");
	return 0;
}