#include <iostream>
#include <vector>
#include <algorithm>
#include <string>

#define REP(i, a, b) for (int i = int(a); i < int(b); i++)
#define dump(val) cerr << __LINE__ << ":\t" << #val << " = " << (val) << endl

using namespace std;

typedef long long int lli;

template<typename T>
vector<T> make_v(size_t a, T b) {
    return vector<T>(a, b);
}

template<typename... Ts>
auto make_v(size_t a, Ts... ts) {
    return vector<decltype(make_v(ts...))>(a, make_v(ts...));
}

int hsh(int n) {
    while (n >= 10) {
        int sum = 0;
        while (n != 0) {
            sum += n % 10;
            n /= 10;
        }
        n = sum;
    }
    return n;
}

int main() {
    int N, K;
    cin >> K >> N;
    vector<bool> isPrime(N + 1, true);
    isPrime[0] = isPrime[1] = false;
    vector<int> Prime;
    vector<int> Phash;
    REP(i, 2, N + 1) {
        if (isPrime[i]) {
            if (i >= K) {
                Prime.push_back(i);
                Phash.push_back(hsh(i));
            }
            for (int j = i * 2; j <= N; j += i) {
                isPrime[j] = false;
            }
        }
    }

    vector<bool> used(10, false);
    int ans = 0;
    int r = 0;
    int cnt = 0;
    REP(i, 0, Prime.size()) {
        while (r < Prime.size() && !used[Phash[r]]) {
            used[Phash[r]] = true;
            r++;
        }
        if (cnt <= r - i) {
            ans = Prime[i];
            cnt = r - i;
        }
        used[Phash[i]] = false;
    }
    cout << ans << endl;
    return 0;
}