#include <iostream>
#include <vector>
#include <cmath>
#include <set>
#include <utility>
#include <sstream>
using namespace std;

int K, N;

// [a, b)に存在する素数を全列挙する.
vector<int> SegmentSieve(int a, int b) {
    vector<int> primes;
    vector<bool> is_prime(b - a, true),
                 is_prime_small(ceil(sqrt(b)) + 1, true);
    is_prime_small[0] = is_prime_small[1] = false;
    if (a == 0) is_prime[0] = is_prime[1] = false;
    if (a == 1) is_prime[0] = false;

    for (int i = 2; i * i < b; i++) {
        if (is_prime_small[i]) {
            for (int j = 2 * i; j * j < b; j += i) is_prime_small[j] = false;
            for (int j = max(2, (a + i - 1) / i) * i; j < b; j += i) is_prime[j - a] = false;
        }
    }
    for (int i = 0; i < is_prime.size(); i++) {
        if (is_prime[i]) primes.push_back(a + i);
    }
    return primes;
}

string itos(int i) {
    ostringstream os;
    os << i;
    return os.str();
}

int Hash(int num) {
    if (num < 10) return num;

    string str_num = itos(num);
    int sum = 0;
    for (int i = 0; i < str_num.size(); i++) {
        sum += str_num[i] - '0';
    }
    return Hash(sum);
}

void Solve() {
    vector<int> primes = SegmentSieve(K, N + 1);
    pair<int, int> answer = make_pair(-1, -1);  // (長さ, 添え字)
    for (int i = 0; i < primes.size(); i++) {
        set<int> hashed;
        int length = 0;
        // たかだか10回
        while (i + length < primes.size()) {
            int h = Hash(primes[i + length]);
            if (hashed.find(h) == hashed.end()) {
                length++;
                hashed.insert(h);

                answer = max(answer, make_pair(length, i));
            } else {
                break;
            }
        }
    }
    cout << primes[answer.second] << endl;
}

int main() {
    cin >> K >> N;

    Solve();

    return 0;
}