source_code: import java.util.Scanner;
  
  
  public class d_169 {
  public static void main(String[] args) {
  	Scanner  sc = new Scanner(System.in);
  	long x=sc.nextLong();
  	long y=sc.nextLong();
  	String s=Long.toBinaryString(x);
  	String p=Long.toBinaryString(y);
  	int id=p.length()-s.length();
  	for (int i =1; i <=id; i++) {
  		s="0"+s;
  	}
  	if(x==y){
  		System.out.println(0);
  		return;
  	}
  	for (int i = 0; i <p.length(); i++) {
  		if(s.charAt(i)!=p.charAt(i)){
  			System.out.println((long)Math.pow(2, s.length()-i)-1);
  			return;
  	}
  }
  }
  }
  