source_code: import java.util.*;
  public class A
  {
      public static void main(String args[])
      {
          Scanner sc=new Scanner(System.in);
          long n=sc.nextLong();
          if(n==0)
          System.out.println(0);
          else if(n%2==1)
          System.out.println((n+1)/2);
          else
          System.out.println(n+1);
      }
  }