#include <iostream>
#include <vector>
#include <queue>
#include <string>
#include <cstring>
#include <cstdio>
#include <sstream>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <set>
#include <map>
#include <list>
#include <iomanip>

#define INF 1000000001
#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define RFOR(i, a, b) for (int i = (a); i >= (b); i--)

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
const double PI = acos(-1.0);

int N, K;
vector<int> primes;

void getprimes(int k, int n)
{
	vector<bool> v(n+1);
	int d=2;
	FOR(d,2,n+1) {
		if (v[d]) continue;
		if (d >= k && d <= n) primes.push_back(d);
		int tmp=d*2;
		while (tmp <= n) {
			v[tmp] = true;
			tmp += d;
		}
	}
}

int gethashval(int p)
{
	while (p >= 10) {
		int x=0, q = p;
		while (q) {
			x += q % 10;
			q /= 10;
		}
		p = x;
	}
	return p;
}

bool collision(vector<int> &used)
{
	FOR(i,1,10) {
		if (used[i]>=2) return true;
	}
	return false;
}

int main()
{
	ios::sync_with_stdio(false);

	cin >> K >> N;
	getprimes(K, N);

	vector<int> hash(primes.size());
	FOR(i,0,primes.size()) {
		hash[i] = gethashval(primes[i]);
	}

	vector<int> used(10, 0);
	int ans=0, maxlen=0, l=0, r=0, hsz=hash.size();
	while (l < hsz) {
		if (r == hsz) {
			used[hash[l++]]--;
		} else if (!collision(used)) {
			used[hash[r++]]++;
		} else {
			used[hash[l++]]--;
		}
		if (!collision(used)) {
			if (maxlen <= r-l) {
				maxlen = r-l;
				ans = primes[l];
			}
		}
	}
	cout << ans << endl;

	return 0;
}