source_code: import java.io.*;
  import java.math.BigInteger;
  import java.util.*;
  
  public class Proj implements Runnable {
  
  	BufferedReader in;
  	PrintWriter out;
  	StringTokenizer str;
  
  	public void solve() throws IOException {
  		long l = nextLong();
  		long r = nextLong();
                  int g = 0;
  		long x = l ^ r;
  		long i = 1;
  		while (x >= i) {
  			i = i * 2;
  		}
  		if (x >= i) {
  			out.println(x);
  		} else
  			out.println(i - 1);
  	}
  
  	public String nextToken() throws IOException {
  		while (str == null || !str.hasMoreTokens()) {
  			str = new StringTokenizer(in.readLine());
  		}
  		return str.nextToken();
  	}
  
  	public int nextInt() throws IOException {
  		return Integer.parseInt(nextToken());
  	}
  
  	public long nextLong() throws IOException {
  		return Long.parseLong(nextToken());
  	}
  
  	public void run() {
  		try {
  			in = new BufferedReader(new InputStreamReader(System.in));
  			out = new PrintWriter(System.out);
  			solve();
  			in.close();
  			out.close();
  		} catch (IOException e) {
  		}
  	}
  
  	public static void main(String[] args) {
  		new Thread(new Proj()).start();
  	}
  }