#include <iostream>
#include <vector>
#include <utility>
using namespace std;

#define N_MAX 200000

int K, N;
bool isnotprime[N_MAX + 10000];
vector<pair<int, int>> mask;

void make_prime() {
	isnotprime[0] = isnotprime[1] = 1;
	for (int i = 2; i * i <= N_MAX; i++) {
		if (!isnotprime[i]) {
			for (int j = i * i; j <= N_MAX; j += i) {
				isnotprime[j] = 1;
			}
		}
	}
}

void make_mask() {
	for (int i = 2; i <= N_MAX; i++) {
		if (!isnotprime[i]) {
			int x = i;
			while (9 < x) {
				int tmp = x;
				x = 0;
				while (tmp) {
					x += tmp % 10;
					tmp /= 10;
				}
			}
			mask.emplace_back(i, 1 << x - 1);
		}
	}
}

int main() {
	make_prime();
	make_mask();
	
	cin >> K >> N;
	
	int len_max = 0, res = 0;
	
	auto it = lower_bound(mask.begin(), mask.end(), make_pair(K, 0));
	while (it != mask.end()) {
		if (N < it->first) break;
		int bit = 0, len = 0;
		for (auto jt = it; jt != mask.end(); jt++) {
			if (bit & jt->second || N < jt->first) {
				if (len_max <= len) {
					len_max = len;
					res = it->first;
				}
				break;
			}
			bit |= jt->second;
			len++;
		}
		it++;
	}
	
	cout << res << '\n';
	
	return 0;
}