source_code: import java.util.*;
  import static java.lang.System.*;
  
  public class D276 {
      Scanner sc = new Scanner(in);
  
  
      public void run() {
          long l=sc.nextLong(),r=sc.nextLong();
  
          long tes=l^r;
  
          int d=0;
          while(tes!=0){
              tes/=2;
              d++;
          }
          ln((1L<<d)-1);
      }
  
  
      public static void main(String[] _) {
          new D276().run();
      }
  
      public static void pr(Object o) {
          out.print(o);
      }
      public static void ln(Object o) {
          out.println(o);
      }
      public static void ln() {
          out.println();
      }
  }