#include <bits/stdc++.h>

using namespace std;

int N, K;
//vector<int> prime;
bool used[10];
int dp[10] = {0};

bool pdp[200000];
vector<int> Prime(){
	vector<int> ret;
	for (int i = 2; i < 200000; i++)
	{
		if (!pdp[i]){
    		ret.push_back(i);
    		for (int j = i + i; j < 200000; j += i)
    		{
    			pdp[j] = true;
    		}
		}
	}
	return ret;
}

int Hash(int num){
    int res = 0;
	while (num > 0){
		res += num % 10;
		num /= 10;
	}
	if (res >= 10) return Hash(res);
	return res;
}

int main(void){
    
    cin >> K >> N;
    
    auto prime = Prime();
    while(prime[0] < K) prime.erase(prime.begin());
    
    int j = 0, p_head = 0, p_len = 0;
    for(int i = 0; i < prime.size() && prime[i] <= N; ++i){
        int i_h = Hash(prime[i]);
        ++dp[i_h];
        while(dp[i_h] > 1){
            int j_h = Hash(prime[j++]);
            --dp[j_h];
        }
        if(i - j + 1 >= p_len){
            p_head = prime[j];
            p_len = i - j + 1;
        }
    }
    
    cout << p_head << endl;
    
    return 0;
}