#include <iostream>
#include <queue>
#include <vector>
#include <tuple>
#include <algorithm>
#include <cmath>
#include <set>

using namespace std;

vector<int> primes(int n)
{
	vector<bool> table(n + 1, true);
	table[0] = table[1] = false;
	int mid = (int)floor(sqrt(n));
	for (int i = 2; i <= mid; i++) {
		if (table[i]) {
			for (int j = i+i; j <= n; j += i)
				table[j] = false;
		}
	}
	vector<int> ans;
	for (int i = 2; i <= n; i++)
		if (table[i])
			ans.push_back(i);
	return ans;
}

int sum_digit(int n)
{
	int i = n;
	int acc = 0;
	for (;;) {
		int m = i % 10;
		int d = i / 10;
		acc += m;
		if (d == 0) {
			if (acc < 10) {
				break;
			} else {
				i = acc;
				acc = 0;
			}
		} else {
			i = d;
		}
	}
	return acc;
}

int main()
{
	int K, N;
	cin >> K >> N;
	vector<int> ps = primes(N);
	auto it = remove_if(ps.begin(), ps.end(), [K](int x) {return x < K; });
	if (it != ps.end())
		ps.erase(it);
	vector<int> ss(ps.size());
	transform(ps.begin(), ps.end(), ss.begin(), sum_digit);
	
	int len = ps.size();
	int ans = 0;
	int ans_len = 0;
	for (int i = 0; i < len; i++) {
		set<int> ks;
		ks.insert(ss[i]);
		int tmp = ps[i];
		int tmp_len = 1;
		for (int j = i+1; j < len; j++) {
			if (ks.find(ss[j]) != ks.end()) {
				if (tmp_len <= (int)ks.size()) {
//					tmp = ps[i];
					tmp_len = ks.size();
				}
				break;
			} else {
				ks.insert(ss[j]);
			}
		}
		tmp_len = ks.size();
		if (ans_len <= tmp_len) {
			ans_len = tmp_len;
			ans = tmp;
		}
	}
	cout << ans << endl;
	return 0;
}