/**
 * Created with IntelliJ IDEA.
 * User: Fcdkbear
 * Date: 11.02.13
 * Time: 16:48
 * To change this template use File | Settings | File Templates.
 */
import java.util.Scanner;

public class test {
    static long[][][][][] dp;
    static String s1,s2;
    static String getbin (long num)
    {
        String tmp="";
        while (num>0)
        {
            long v=(num%2);
            tmp+=(char)(v+'0');
            num/=2;
        }
        String res="";
        int n=tmp.length();
        for (int i=n-1; i>=0; --i)
            res+=tmp.charAt(i);
        return res;
    }
    static int len;
    static long rec(int p, int fl1, int fl2, int fr1, int fr2)
    {
        if (p==len)
            return 0;
        if (dp[p][fl1][fl2][fr1][fr2] != -1)
            return dp[p][fl1][fl2][fr1][fr2];
        int min1 = 0, max1 = 1;
        if ((fl1 == 0) && (s1.charAt(p) == '1'))
            min1 = 1;
        if ((fl2 == 0) && (s2.charAt(p) == '0'))
            max1 = 0;
        int min2 = 0, max2 = 1;
        if ((fr1 == 0) && (s1.charAt(p) == '1'))
            min2 = 1;
        if ((fr2 == 0) && (s2.charAt(p) == '0'))
            max2 = 0;
        long res = 0;
        for (int i=min1; i<=max1; ++i)
        for (int j=min2; j<=max2; ++j)
        {
            int v = (i ^ j);
            long toadd = 0;
            if (v == 1) {
                int step = len - p - 1;
                toadd = (1L << step);
            }
            int nfl1 = fl1, nfl2 = fl2, nfr1 = fr1, nfr2 = fr2;
            if (i > s1.charAt(p) - '0')
                nfl1 = 1;
            if (i < s2.charAt(p) - '0')
                nfl2 = 1;
            if (j > s1.charAt(p) - '0')
                nfr1 = 1;
            if (j < s2.charAt(p) - '0')
                nfr2 = 1;
            long res1= toadd + rec(p + 1, nfl1, nfl2, nfr1, nfr2);
            res = Math.max(res,res1);
        }
        return dp[p][fl1][fl2][fr1][fr2] = res;
    }
    public static void main(String [] args)
    {
        dp=new long[70][2][2][2][2];
        for (int i=0; i<70; ++i)
            dp[i]=new long[2][2][2][2];
        for (int i = 0; i < 70; ++i)
            for (int j=0; j<2; ++j)
                dp[i][j] = new long[2][2][2];
        for (int i = 0; i < 70; ++i)
            for (int j = 0; j < 2; ++j)
                for (int k=0; k<2; ++k)
                    dp[i][j][k] = new long[2][2];
        for (int i = 0; i < 70; ++i)
            for (int j = 0; j < 2; ++j)
                for (int k = 0; k < 2; ++k)
                    for (int c=0; c<2; ++c)
                        dp[i][j][k][c] = new long[2];
        for (int i = 0; i < 70; ++i)
            for (int j = 0; j < 2; ++j)
                for (int k = 0; k < 2; ++k)
                    for (int c = 0; c < 2; ++c)
                        for (int l=0; l<2; ++l)
                            dp[i][j][k][c][l]=-1;
        Scanner sc = new Scanner(System.in);
        long l=sc.nextLong();
        long r=sc.nextLong();
        s1=getbin(l);
        s2=getbin(r);
        while (s1.length()<s2.length())
            s1="0"+s1;
        len=s1.length();
        //System.out.println(s1);
        //System.out.println(s2);
        long res=rec(0,0,0,0,0);
        System.out.println(res);
    }
}