import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		// TODO Auto-generated method stub
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int s;
		if(n % 2 == 1){
			s = (n + 1) / 2;
			System.out.println(s);
		}else if(n % 2 == 0){
			s = n + 1;
			System.out.println(s);
		}
	}

}
/**************************************************************
	Problem: 1558
	User: admin
	Language: Java
	Result: Accepted
	Time:4260 ms
	Memory:40632 kb
****************************************************************/