source_code: import java.io.BufferedReader;
  import java.io.BufferedWriter;
  import java.io.IOException;
  import java.io.InputStreamReader;
  import java.io.OutputStreamWriter;
  import java.io.PrintWriter;
  import java.util.StringTokenizer;
  
  
  public class D {
  	
  	static StringTokenizer st;
  	static BufferedReader in;
  	public static void main(String[] args) throws IOException {
  		in = new BufferedReader(new InputStreamReader(System.in));
  		PrintWriter pw = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
  		long L = nextLong();
  		long R = nextLong();
  		if (L==R) {
  			System.out.println(0);
  			return;
  		}
  		String s1 = Long.toBinaryString(L), s2 = Long.toBinaryString(R);
  		while (s1.length() != s2.length())
  			s1 = "0"+s1;
  		for (int i = 0; i < s1.length(); i++) {
  			if (s1.charAt(i) != s2.charAt(i)) {
  				int pow = s1.length()-i;
  				System.out.println((long)Math.pow(2, pow)-1);
  				return;
  			}
  		}
  		pw.close();
  	}
  	private static int nextInt() throws IOException{
  		return Integer.parseInt(next());
  	}
  	
  	private static long nextLong() throws IOException{
  		return Long.parseLong(next());
  	}
  	
  	private static double nextDouble() throws IOException{
  		return Double.parseDouble(next());
  	}
  	
  	private static String next() throws IOException {
          while (st == null || !st.hasMoreTokens()) {
              st = new StringTokenizer(in.readLine());
          }
          return st.nextToken();
      }
  }
  