#include <iostream>
#include <vector>
#include <set>
#include <queue>
#include <algorithm>
#include <numeric>
#include <cstring>
#include <cmath>
using namespace std;
typedef long long ll;
 
int h(int n){
	if(n == 0)return 0;
	if(n % 9 == 0)return 9;
 
	return n % 9;
}
 
bool isp[200010];
vector<int> getPrimes(int K, int N){
	for(int i=0;i<=N;i++)isp[i] = true;
 
	isp[0] = isp[1] = false;
	for(int p=2;p*p<=N;p++)if(isp[p]){
		for(int k=p*p;k<=N;k+=p)isp[k] = false;
	}
 
	vector<int> res;
	for(int i=K;i<=N;i++)if(isp[i])res.push_back(i);
 
	return res;
}
 
int main() {
	int K, N;
	cin >> K >> N;
 
	vector<int> primes = getPrimes(K, N);
 
	int maxi = 0;
	int res = 0;
	for(int i=0;i<primes.size();i++){
		set<int> used;
 
		int cnt = 0;
		for(int j=i;j<primes.size();j++){
			int hs = h(primes[j]);
			if(used.count(hs))break;
 
			used.insert(hs);
			++cnt;
		}
 
		if(cnt >= maxi){
			maxi = cnt;
			res = primes[i];
		}
	}
 
	cout << res << endl;
	return 0;
}