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

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int k = sc.nextInt();
        int n = sc.nextInt();
        HashSet<Integer> hashes = new HashSet<>();
        ArrayDeque<Integer> deq = new ArrayDeque<>();
        boolean[] isNotPrimes = new boolean[n + 1];
        int max = 0;
        int ans = 0;
        for (int i = 2; i <= n; i++) {
            if (isNotPrimes[i]) {
                continue;
            }
            for (int j = 2; j * i <= n; j++) {
                isNotPrimes[j * i] = true;
            }
            if (i < k) {
                continue;
            }
            int h = getHash(i);
            if (hashes.contains(h)) {
                int x;
                while (h != (x = getHash(deq.poll()))) {
                    hashes.remove(x);
                }
                deq.add(i);
            } else {
                hashes.add(h);
                deq.add(i);
            }
            if (max <= hashes.size()) {
                max = hashes.size();
                ans = deq.peek();
            }
        }
        System.out.println(ans);
    }
    
    static int getHash(int x) {
        if (x < 10) {
            return x;
        } else {
            int sum = 0;
            while (x > 0) {
                sum += x % 10;
                x /= 10;
            }
            return getHash(sum);
        }
    }
}

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 {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
}