source_code: import java.util.*;
  
  public class D {
  
  	public static void main(String[] args) {
  		Scanner sc = new Scanner(System.in);
  		long L = sc.nextLong();
  		long R = sc.nextLong();
  		long res = Math.max(2 * Long.highestOneBit(L ^ R) - 1, 0);
  		System.out.println(res);
  	}
  }
  