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

public class Main {
    public static void main(String[] args) throws Exception {
        Scanner sc = new Scanner();
        int k = sc.nextInt();
        int n = sc.nextInt();
        boolean[] isNotPrimes = new boolean[n + 1];
        isNotPrimes[1] = true;
        ArrayList<Integer> primes = new ArrayList<>();
        for (int i = 2; i <= n; i++) {
            if (!isNotPrimes[i]) {
                if (i >= k) {
                    primes.add(i);
                }
                for (int j = 2; j * i <= n; j++) {
                    isNotPrimes[j * i] = true;
                }
            }
        }
        int left = 0;
        HashSet<Integer> exists = new HashSet<>();
        int max = 0;
        int ans = 0;
        for (int i = 0; i < primes.size(); i++) {
            int hash = getHash(primes.get(i));
            if (exists.contains(hash)) {
                while (true) {
                    int tmp = getHash(primes.get(left));
                    if (tmp == hash) {
                        left++;
                        break;
                    }
                    exists.remove(tmp);
                    left++;
                }
            } else {
                exists.add(hash);
            }
            if (max <= exists.size()) {
                max = exists.size();
                ans = primes.get(left);
            }
        }
        System.out.println(ans);
    }
    
    static int getHash(int x) {
        if (x < 10) {
            return x;
        }
        int ans = 0;
        while (x > 0) {
            ans += x % 10;
            x /= 10;
        }
        return getHash(ans);
    }
}

class Utilities {
    static String arrayToLineString(Object[] arr) {
        return Arrays.stream(arr).map(x -> x.toString()).collect(Collectors.joining("\n"));
    }
    
    static String arrayToLineString(int[] arr) {
        return String.join("\n", Arrays.stream(arr).mapToObj(String::valueOf).toArray(String[]::new));
    }
}
class Scanner {
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    StringTokenizer st = new StringTokenizer("");
    StringBuilder sb = new StringBuilder();
    
    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 int[] nextIntArray() throws Exception {
        return Stream.of(br.readLine().split(" ")).mapToInt(Integer::parseInt).toArray();
    }
    
    public String next() throws Exception {
        while (!st.hasMoreTokens()) {
            st = new StringTokenizer(br.readLine());
        }
        return st.nextToken();
    }
    
}