#include <iostream>
#include <cstring>
#include <vector>
#include <algorithm>

typedef std::pair<int, int> P;
const int max = 200001;

bool isPrime[max];
std::vector<P> v;

void init(){
	memset(isPrime, -1, sizeof(isPrime));

	isPrime[0] = false;
	isPrime[1] = false;

	for (int i = 2; i*i <= max; i++){
		if (!isPrime[i])continue;
		for (int j = i * 2; j < max; j += i)isPrime[j] = false;
	}

	for (int i = 2; i < max; i++){
		if (isPrime[i])v.push_back(P(i, i % 9));
	}
}

int main(){
	init();

	int n, k;
	std::cin >> n >> k;

	int s = 0, e = v.size() - 1;
	while (v[s].first < n)s++;
	while (v[e].first > k)e--;

	int ans = 0, max_size = 0;

	for (int i = e; i >= s; i--){
		int cnt[9], size = 0;
		memset(cnt, 0, sizeof(cnt));

		int j = 0;
		while (cnt[v[i + j].second] == 0 && i + j <= e){
			cnt[v[i + j].second]++;
			size++;
			j++;
		}
		if (size > max_size)ans = v[i].first, max_size = size;
	}

	std::cout << ans << std::endl;

	return 0;
}