import java.io.*;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        System.out.println(getMin(sc.nextInt(), sc.nextInt()));
    }
    
    static int getMin(int x, int y) {
        if (x > y) {
            return getMin(y, x);
        }
        int left = getLeft(y);
        if ((x & left) == 0) {
            return x;
        } else {
            return left - 1;
        }
    }
    
    static int getLeft(int x) {
        int count = 0;
        while (x > 0) {
            count++;
            x >>= 1;
        }
        return 1 << (count - 1);
    }
}

class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    
    public Scanner() throws Exception {
        
    }
    
    public int nextInt() throws Exception {
        return Integer.parseInt(next());
    }
    
    public long nextLong() throws Exception {
        return Long.parseLong(next());
    }
    
    public double nextDouble() throws Exception {
        return Double.parseDouble(next());
    }
    
    public String next() throws Exception {
        if (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
}