/*
                   _ooOoo_
                  o8888888o
                  88" . "88
                  (| -_- |)
                  O\  =  /O
               ____/`---'\____
             .'  \\|     |//  `.
            /  \\|||  :  |||//  \
           /  _||||| -:- |||||-  \
           |   | \\\  -  /// |   |
           | \_|  ''\---/''  |   |
           \  .-\__  `-`  ___/-. /
         ___`. .'  /--.--\  `. . __
      ."" '<  `.___\_<|>_/___.'  >'"".
     | | :  `- \`.;`\ _ /`;.`/ - ` : | |
     \  \ `-.   \_ __\ /__ _/   .-` /  /
======`-.____`-.___\_____/___.-`____.-'======
                   `=---='
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
            pass System Test!
*/
#include <bits/stdc++.h>
using namespace std;

template <typename T>
std::ostream &operator<<(std::ostream &out, const std::vector<T> &v) {
  if (!v.empty()) {
    out << '[';
    std::copy(v.begin(), v.end(), std::ostream_iterator<T>(out, ", "));
    out << "\b\b]";
  }
  return out;
}
template <typename T1, typename T2>
std::ostream &operator<<(std::ostream &out, const std::pair<T1, T2> &p) {
  out << "[" << p.first << ", " << p.second << "]";
  return out;
}
template <class T, class U>
void chmin(T &t, U f) {
  if (t > f) t = f;
}
template <class T, class U>
void chmax(T &t, U f) {
  if (t < f) t = f;
}
template <typename T>
void uniq(vector<T> &v) {
  v.erase(unique(v.begin(), v.end()), v.end());
}

vector<int> primes;

void eratosthenes(int N) {
  vector<bool> is_prime(N + 1, true);
  is_prime[0] = false;
  is_prime[1] = false;
  for (int i = 2; i <= N; ++i)
    if (is_prime[i]) {
      primes.push_back(i);
      for (int j = i * 2; j <= N; j += i) {
        is_prime[j] = false;
      }
    }
}

int64_t get_min_divisor(int64_t t) {
  for (int p : primes)
    if (t % p == 0)
      return p;
    else if (p > sqrt(t + 1))
      break;
  return t;
}

int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);

  eratosthenes(1e5);

  int64_t L, H;
  cin >> L >> H;

  int64_t ans = -1;
  for (int i = primes.size() - 1; i >= 0; --i) {
    int64_t prime = primes[i];
    int64_t h = H / prime * prime;
    int64_t l = max(L, prime * prime);
    for (; h >= l; h -= prime) {
      int64_t divisor = get_min_divisor(h / prime);
      if (divisor < prime) {
        continue;
      }
      if (ans < 0) ans = h;
      break;
    }
  }
  cout << ans << endl;
}