source_code: import java.util.Scanner;
  
  public class D {
  
      public static void main(String[] args) {
          Scanner s = new Scanner(System.in);
          long l = s.nextLong();
          long r = s.nextLong();
          long a = l ^ r;
          long b = a;
          while (b != 0) {
              a = b;
              b = (b-1) & b;
          }
          if (a != 0) {
              a = (a << 1) - 1;
          }
          System.out.println(a);
      }
  
  }
  