#include <bits/stdc++.h>
using namespace std;
using i64 = int64_t;
using vi = vector<i64>;
using vvi = vector<vi>;

int numroot(int k) {
    if (k == 0) return 0;
    if (k % 9 == 0) return 9;
    return k % 9;
}

vi ps(202020, 1);

int main() {
    ps[0] = ps[1] = 0;
    for (int i = 2; i < 202020; i++) {
        if (ps[i] == 0) continue;
        for (int j = 2; i * j < 202020; j++) {
            ps[i * j] = 0;
        }
    }

    int k, n;
    cin >> k >> n;
    vi qs;
    for (int i = k; i <= n; i++) {
        if (ps[i]) qs.push_back(i);
    }

    set<int> roots;

    int l = 0, r = 0;
    int sz = 0, ans;
    while (1) {
        if (r >= qs.size()) break; 
        int root = numroot(qs[r]);
        if (roots.count(root) == 0) {
            r++;
            roots.insert(root);
            if (roots.size() >= sz) {
                sz = roots.size();
                ans = qs[l];
            }
        } else {
            while (1) {
                int root2 = numroot(qs[l]);
                roots.erase(root2);
                l++;
                if (root == root2) break;
            }
        }
    }
    cout << ans << endl;
}