import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n_1 = sc.nextInt();
        if(n_1 >= 2 || 3 / n_1 != 0){
            System.out.println(n_1 + 1);
        }else if(n_1 >= 2 || n_1 / 2 == 0){
            System.out.println(n_1);
        }
     
        }
    }