source_code: 
  import java.util.Scanner;
  
  public class D {
  	public static void main(String [] args){
  		Scanner in = new Scanner(System.in);
  		long a = in.nextLong();
  		long b = in.nextLong();
  		String sa = Long.toBinaryString(a);
  		String sb = Long.toBinaryString(b);
  		long ans = 0;
  		if(sb.length()-sa.length()>0){
  			for(int i = 0 ; i < sb.length() ; i++){
  				ans += 1l<<i;
  			}
  			System.out.println(ans);
  		}
  		else{
  			int num = -1 ;
  			for(int i = 62 ; i >= 0 ; i--){
  				if((b & 1l << i) != 0 && ((~a) & (1l << i)) != 0){
  					num = i;
  					break;
  				}
  			}
  			ans = 0;
  			if(num!=-1) for(int i = 0 ; i <= num ; i ++){
  				ans += 1l<<i;
  			}
  			System.out.println(ans);
  	}
  	}
  
  }