#include <cstdio>
#include <iostream>
#include <string>
#include <sstream>
#include <stack>
#include <algorithm>
#include <cmath>
#include <queue>
#include <map>
#include <set>
#include <cstdlib>
#include <bitset>
#include <tuple>
#include <assert.h>
#include <deque>
#include <bitset>
#include <iomanip>
#include <limits>
#include <chrono>
#include <random>
#include <array>
#include <unordered_map>
#include <functional>
#include <complex>
#include <numeric>
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
constexpr long long MAX = 5100000;
constexpr long long INF = 1LL << 60;
constexpr int inf = 1000000007;
constexpr long long mod = 1000000007LL;
//constexpr long long mod = 998244353LL;
const long double PI = acos((long double)(-1));

using namespace std;
typedef unsigned long long ull;
typedef long long ll;
typedef long double ld;

vector<bool> isprime;

void eratos(ll n) {
	isprime.resize(n + 1);
	for (ll i = 0; i <= n; i++) {
		isprime[i] = true;
	}
	isprime[0] = false;
	isprime[1] = false;
	for (ll i = 2; i * i <= n; i++) {
		if (isprime[i]) {
			ll j = i + i;
			while (j <= n) {
				isprime[j] = false;
				j = j + i;
			}
		}
	}
}

int main()
{
	/*
	cin.tie(nullptr);
	ios::sync_with_stdio(false);
	*/

	eratos(MAX / 10);
	int k, n; cin >> k >> n;
	vector<int> p;
	for (int i = k; i <= n; i++) if (isprime[i]) p.emplace_back(i);
	vector<int> v(p.size()); for (int i = 0; i < p.size(); i++) v[i] = p[i] % 9;
	int rg = 0;
	int len = 0;
	int res = 0;
	vector<bool> used(10, false);
	for (int lf = 0; lf < p.size(); lf++) {
		while (rg < p.size() and !used[v[rg]]) {
			used[v[rg]] = true;
			rg++;
		}
		if (chmax(len, rg - lf)) res = p[lf];
		else if (len == rg - lf) chmax(res, p[lf]);
		if (lf == rg) rg++;
		else used[v[lf]] = false;
	}
	cout << res << endl;
	return 0;
}