#include <iostream>
#include <cstdio>
#include <vector>
#include <algorithm>
#include <utility>

using namespace std;

int get_hash(int num) {

	int hash = 0;
	while (num > 0) {
		hash += num % 10;
		num /= 10;
	}
	if (hash >= 10) {
		return get_hash(hash);
	}

	return hash;
}

int main() {
	int k, n;
	cin >> k >> n;

	vector<bool> prime_check(n + 1, true);
	vector< pair<int, int> > primes;

	prime_check[0] = prime_check[1] = false;

	for (int i = 4; i <=n; i += 2) {
		prime_check[i] = false;
	}

	for (int i = 3; i * i <= n; i += 2) {
		if (prime_check[i]) {
			for (int j = i + i; j <= n; j += i) {
				prime_check[j] = false;
			}
		}
	}

	for (int i = k; i <= n; i++) {
		if (prime_check[i]) {
			primes.push_back(make_pair(i, get_hash(i)));
		}
	}

	int max_len = 0;
	int ans = 0;

	for (int i = 0; i < primes.size(); i++) {
		int bits = 0;
		int len = 0;
		for (int j = 0; j < 10 && i + j < primes.size(); j++) {
			if ((bits & (1 << primes[i + j].second)) == 0) {
				bits |= 1 << primes[i + j].second;
				len++;
			} else {
				break;
			}
		}
		// printf("%d %d\n", primes[i].first, len);
		if (max_len <= len) {
			max_len = len;
			ans = primes[i].first;
		}
	}

	cout << ans << endl;
	return 0;
}