#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();
    
    for(int i = 0; i < prime.size(); ++i){
        int j, h_num;
        for(j = 0; j < 10; ++j) used[j] = false;
        for(j = 0; i + j < prime.size() && !used[(h_num = Hash(prime[i + j]))]; ++j) used[h_num] = true;
        if(dp[j] < prime[i]) dp[j] = prime[i]; 
    }
    
    for(int i = 9; i >= 0; --i){
        if(dp[i] != 0){
            cout << dp[i] << endl;
            break;
        }
    }
    
    return 0;
}