import java.io.*;
import java.util.Scanner;

public class Solution {
    public static void main(String[] args) throws Exception {
        //write your code here
        Scanner scanner = new Scanner(System.in);
        int num = scanner.nextLine();
        if (n > 0) {
            n = 2 * n;
            System.out.println(n);
        }
        else if ( n == 0 )
            System.out.println(0);
        else {
            n = n + 1;
            System.out.println(0);
        }
    }


    }