#include <iostream>
#include <vector>

struct Prime {
    int max_n;
    std::vector<int> primes;
    std::vector<bool> isp;

    explicit Prime(int max_n)
        : max_n(max_n), isp(max_n + 1, true) {
        isp[0] = isp[1] = false;
        for (int i = 2; i * i <= max_n; ++i) {
            if (isp[i]) {
                for (int j = i; i * j <= max_n; ++j) {
                    isp[i * j] = false;
                }
            }
        }

        for (int p = 2; p <= max_n; ++p) {
            if (isp[p]) primes.push_back(p);
        }
    }

    template <class T>
    bool isprime(T n) const {
        if (n <= max_n) return isp[n];
        for (T p : primes) {
            if (p * p > n) break;
            if (n % p == 0) return false;
        }
        return true;
    }

    template <class T>
    std::vector<std::pair<T, int>> factorize(T n) const {
        std::vector<std::pair<T, int>> facts;
        for (T p : primes) {
            if (p * p > n) break;
            if (n % p != 0) continue;
            int exp = 0;
            while (n % p == 0) {
                n /= p;
                ++exp;
            }
            facts.emplace_back(p, exp);
        }
        if (n > 1) {
            facts.emplace_back(n, 1);
        }
        return facts;
    }

    template <class T>
    static std::vector<T> divisors(T n) {
        std::vector<T> ret;
        for (T p = 1; p * p <= n; ++p) {
            if (n % p != 0) continue;
            ret.push_back(p);
            if (n / p == p) continue;
            ret.push_back(n / p);
        }
        return ret;
    }
};

const Prime P(200000);

void solve() {
    int l, r;
    std::cin >> l >> r;

    std::vector<int> ps;
    for (int p = l; p <= r; ++p) {
        if (P.isprime(p)) ps.push_back(p);
    }

    int n = ps.size();

    int max = 0, mp = -1;
    for (int i = 0; i < n; ++i) {
        std::vector<bool> used(9, false);

        int len = 0;
        while (i + len < n && !used[ps[i + len] % 9]) {
            used[ps[i + len] % 9] = true;
            ++len;
        }

        if (len >= max) {
            max = len;
            mp = ps[i];
        }
    }

    std::cout << mp << "\n";
}

int main() {
    std::cin.tie(nullptr);
    std::ios::sync_with_stdio(false);

    solve();

    return 0;
}