#include <bits/stdc++.h>

using namespace std;

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

void Prime(){
    int i, j, k;
    if(K <= 2) prime.push_back(2);
	for(i = 3; i <= 200000; i += 2){
		k = 0;
		for(j = 3; j <= sqrt(i); j += 2){
			if(i % j == 0){
				k = 1;
				break;
			}
		}
		if(k == 0 && K <= i && i <= N) prime.push_back(i);
	}
	return;
}

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;
    
    Prime();
    
    int j = 0, p_head = 0, p_len = 0;
    for(int i = 0; i < prime.size(); ++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;
}