#include <iostream>
#include <iomanip>
#include <vector>
#include <algorithm>
#include <functional>
#include <cmath>
#include <string>
#include <queue>
#include <map>
#include <bitset>
#include <set>
#include <stack>
#include <numeric>
#include <unordered_map>
#include <random>

using namespace std;

using ll = long long;
using vi = vector<int>;
using vvi = vector<vi>;
using vl = vector<ll>;
using vvl = vector<vl>;
using vb = vector<bool>;
using vvb = vector<vb>;
using vd = vector<double>;
using vs = vector<string>;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pdd = pair<double, double>;
using vpii = vector<pii>;
using vpll = vector<pll>;
using vpdd = vector<pdd>;
const int inf = (1 << 30) - 1;
const ll INF = 1LL << 60;
//const int MOD = 1000000007;
const int MOD = 998244353;

vector<bool> Eratosthenes(int N) {
	vector<bool> isPrime(N + 1, true);
	isPrime[0] = isPrime[1] = false;

	for (int p = 2; p * p <= N; ++p) {
		if (!isPrime[p]) continue;

		for (int q = p * 2; q <= N; q += p) {
			isPrime[q] = false;
		}
	}
	return isPrime;
}
ll sumDigits(ll x) {
	int ret = 0;
	do {
		ret += x % 10;
		x /= 10;
	} while (x > 0);
	return ret;
}
int f(int x) {
	if (x < 10) return x;
	return f(sumDigits(x));
}

int main() {
	int k, n;
	cin >> k >> n;
	vb isPrime = Eratosthenes(n);
	vpii p;
	for (int i = k; i <= n; i++) {
		if (isPrime[i]) {
			p.push_back({ i, f(i) });
		}
	}
	int ans = 0;
	int maxsize = 0;
	set<int> st;
	int r = 0;
	for (int l = 0; l < p.size(); l++) {
		while (r < p.size() && st.find(p[r].second) == st.end()) {
			st.insert(p[r].second);
			r++;
		}

		if (st.size() >= maxsize) {
			ans = p[l].first;
			maxsize = st.size();
		}
		if (l == r) r++;
		else st.erase(p[l].second);
	}
	cout << ans << endl;
	
	return 0;
}