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

public class Main {

    public static void main(String[] args) throws Exception {

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

        int K = Integer.parseInt(br.readLine());
        int N = Integer.parseInt(br.readLine());

        int sc = (int) Math.sqrt(N);

        int[] d = new int[N + 1];

        d[0] = 1;
        d[1] = 1;

        for (int i = 2; i <= sc; i++) {
            if (d[i] != 0) {
                continue;
            }
            for (int j = i; j < N; j++) {
                int dest = i * j;
                if (dest > d.length - 1) {
                    break;
                }
                d[i * j] = 1;
            }
        }

        ArrayList<Integer> list = new ArrayList();
        for (int i = 0; i < 10; i++) {
            list.add(0);
        }

        for (int i = K; i <= N; i++) {
            if (d[i] != 0) {
                continue;
            }
            int tmp = change(i);
            if (list.get(tmp) < i) {
                list.set(tmp, i);
            }
        }

        list.sort(null);

        for (int i = 0; i < list.size(); i++) {
            int tmp = list.get(i);
            if (tmp != 0) {
                System.out.println(tmp);
                return;
            }
        }
    }

    private static int change(int source) {
        char[] c = Integer.toString(source).toCharArray();
        while (c.length != 1) {

            source = 0;
            if (c.length > 1) {
                for (int i = 0; i < c.length; i++) {
                    source += Integer.parseInt(String.valueOf(c[i]));
                }
            } else {
                source += Integer.parseInt(String.valueOf(c));
                break;
            }

            c = Integer.toString(source).toCharArray();
        }

        return source;
    }
}