import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.LinkedList;
import java.util.Scanner;
import java.util.Set;
import java.util.TreeSet;

public class Main {
	
	public static final int hash(int n){
		if(n < 10){
			return n;
		}else{
			int ret = 0;
			for(final char c : (n + "").toCharArray()){
				ret += Character.getNumericValue(c);
			}
			
			return hash(ret);
		}
	}
	
	public static void main(String[] args){
		Scanner sc = new Scanner(System.in);
		
		final int K = sc.nextInt();
		final int N = sc.nextInt();
		
		boolean[] is_prime = new boolean[N + 1];
		Arrays.fill(is_prime, true);
		is_prime[0] = is_prime[1] = false;
		LinkedList<Integer> primes = new LinkedList<Integer>();
		for(int p = 2; p <= N; p++){
			if(is_prime[p]){
				if(p >= K){
					primes.add(p);
				}
				
				for(int j = 2 * p; j <= N; j += p){
					is_prime[j] = false;
				}
			}
		}
		
		boolean[] hash_use = new boolean[10];
		LinkedList<Integer> hash_using = new LinkedList<Integer>();
		LinkedList<Integer> prime_using = new LinkedList<Integer>();
		
		int max_len = 1, min = Integer.MAX_VALUE;
		for(final int prime : primes){
			final int hash = hash(prime);
			
			if(hash_use[hash]){
				while(true){
					final int removed_prime = prime_using.poll();
					if(max_len <= hash_using.size()){
						max_len = hash_using.size();
						min = removed_prime;
					}
					
					final int removed_hash = hash_using.poll();
					hash_use[removed_hash] = false;

					
					if(removed_hash == hash){
						break;
					}
				}
			}
			
			hash_using.add(hash);
			prime_using.add(prime);
			hash_use[hash] = true;
			
			//System.out.println(hash + " : " + hash_using + "="  + prime_using + " " + prime + " " + min);
		}
		
		if(!hash_using.isEmpty() && max_len <= hash_using.size()){
			max_len = hash_using.size();
			min = prime_using.getFirst();
		}
		
		
		System.out.println(min);
	}
	
}