source_code: import java.util.*;
  
  
  
  public class Code {
  	public Code(){}
  	public static void main(String args[]){
  		Scanner QQQ=new Scanner(System.in);
  		long l=QQQ.nextLong();
  		long r=QQQ.nextLong();
  		long ans=l^r;
  		int a[]=new int [70];
  		int b[]=new int [70];
  		int n=0,m=0;
  		while (l!=0){
  			a[m]=(int)(l%2);
  			l/=2;
  			m++;
  		}
  		while (r!=0){
  			b[n]=(int)(r%2);
  			r/=2;
  			n++;
  		}
  		m--;n--;
  		long deg[]=new long [70];
  		deg[0]=1;
  		for (int i=1;i<=62;i++) deg[i]=deg[i-1]*2;
  		for (int i=n;i>=0;i--) 
  			if (b[i]==1&&a[i]==0){
  				System.out.println(deg[i+1]-1);
  				return;
  			}
  		System.out.println(ans);
  	}
  }