#include <bits/stdc++.h>
#include "bits/stdc++.h"
#include <iostream>
#include <iomanip>
#include <vector>
#include <algorithm>
#include <string>
#include <sstream>
#include <cmath>
#include <stack>
#include <queue>
#include <cctype>
#include <stdio.h>
#include <map>
#include <unordered_map>
#include <string.h>
#include <utility>

typedef long long ll;
const int INF = 1e8;

#define rep(i,n) for(ll i=0;i<(ll)(n);i++)
using namespace std;

typedef pair<int, int> P;

bool prime[200001];

vector<int> prime_numbe;

bool check[10];

void check_inite() {
	for (int i = 0; i < 10; i++) {
		check[i] = false;
	}
}
void shieve(int x, int y) {
	for (int i = 2; i <= y; i++) {
		if (!prime[i]) {

			if (i >= x) {
				prime_numbe.push_back(i);
			}
			for (int j = i * 2; j <= y; j += i) {
				prime[j] = true;
			}
		}
	}
}

int has(int x) {
	int s = 0;

	while (x / 10 != 0) {
		s = x % 10;

		x /= 10;

		x += s;
	}

	return x;
}

int main() {

	int k, n;
	cin >> k >> n;

	shieve(k, n);

	/*	for (int i = 0; i < prime_numbe.size(); i++) {
	 cout << prime_numbe[i] << endl;
	 }*/
	int left = 0, right = 0;

	int ct = 0;

	int ans = 0;

	int tmp = 0;

	for (left = 0; left < prime_numbe.size(); left++) {

		for (right = left; right < prime_numbe.size(); right++) {

			int hashnum = has(prime_numbe[right]);

			if (!check[hashnum]) {
				ct++;
				check[hashnum] = true;

				/*cout << hashnum << " " << prime_numbe[right] << endl;*/

			} else {
				break;

			}

		}
		if (tmp <= ct) {
			ans = max(ans, prime_numbe[left]);
/*
			cout << ans << endl;*/
			tmp = ct;
		}
		ct = 0;
		check_inite();
	}

	cout << ans << endl;

	return 0;
}