#include <bits/stdc++.h>
using namespace std;

bool is_prime(int n) {
    if (n == 1)
        return false;
    for (int i = 2; i * i <= n; i++)
        if (n % i == 0)
            return false;
    return true;
}

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

    vector<int> V;
    for (int i = K; i <= N; i++) {
        if (is_prime(i))
            V.push_back(i);
    }

    int ans = 0, len = 0;
    for (int i = 0; i < V.size(); i++) {
        int memo[10] = {};
        memo[V[i] % 9] = 1;
        for (int l = i + 1; l <= V.size(); l++) {
            if (l == V.size() || memo[V[l] % 9]) {
                if (l - i >= len) {
                    ans = V[i];
                    len = l - i;
                }
                break;
            } else {
                memo[V[l] % 9] = 1;
            }
        }
    }
    cout << ans << endl;
}