#if __INCLUDE_LEVEL__ == 0

#include __BASE_FILE__

void Solve() {
  int64_t L, R;
  IN(L, R);
  auto ps = kactl::eratosthenes();
  ps.erase(ps.begin());
  for (int64_t a : ps) {
    if (a * a * (a + 2) * (a + 4) > R)
      break;
    for (int64_t b : ps) {
      if (b <= a)
        continue;
      if (a * a * b * (b + 2) > R)
        break;
      int64_t c = R / (a * a * b);
      if (c % 2 == 0)
        --c;
      for (; c > b && a * a * b * c >= L; c -= 2)
        if (kactl::isPrime(c)) {
          OUT(a * a * b * c);
          return;
        }
    }
  }
  OUT(-1);
}

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

  Solve();
}

#elif __INCLUDE_LEVEL__ == 1

#include <bits/stdc++.h>

template <class T>
concept MyRange =
    std::ranges::range<T> &&
    !std::convertible_to<T, std::string_view> &&
    !std::convertible_to<T, std::filesystem::path>;

template <class T>
concept MyTuple = std::__is_tuple_like<T>::value && !MyRange<T>;

namespace std {

istream& operator>>(istream& is, MyRange auto&& r) {
  for (auto&& e : r) {
    is >> e;
  }
  return is;
}

istream& operator>>(istream& is, MyTuple auto&& t) {
  apply([&](auto&... xs) { (is >> ... >> xs); }, t);
  return is;
}

ostream& operator<<(ostream& os, MyRange auto&& r) {
  auto sep = "";
  for (auto&& e : r) {
    os << exchange(sep, " ") << forward<decltype(e)>(e);
  }
  return os;
}

ostream& operator<<(ostream& os, MyTuple auto&& t) {
  auto sep = "";
  apply([&](auto&... xs) { ((os << exchange(sep, " ") << xs), ...); }, t);
  return os;
}

}  // namespace std

template <class T>
class OneBased {
 public:
  explicit OneBased(T&& x) : ref_(std::forward<T>(x)) {}

  template <class... Ts>
  requires(sizeof...(Ts) > 1)
      OneBased(Ts&&... xs) : ref_(std::forward_as_tuple(std::forward<Ts>(xs)...)) {}

  friend std::istream& operator>>(std::istream& is, OneBased x) {
    if constexpr (MyRange<T>) {
      for (auto&& e : x.ref_) {
        is >> ::OneBased(e);
      }
    } else if constexpr (MyTuple<T>) {
      std::apply([&](auto&... xs) { (is >> ... >> ::OneBased(xs)); }, x.ref_);
    } else {
      is >> x.ref_;
      --x.ref_;
    }
    return is;
  }

  friend std::ostream& operator<<(std::ostream& os, OneBased x) {
    if constexpr (MyRange<T>) {
      auto f = [](auto&& e) { return ::OneBased(std::forward<decltype(e)>(e)); };
      os << (x.ref_ | std::views::transform(f));
    } else if constexpr (MyTuple<T>) {
      std::apply([&](auto&... xs) { os << std::tuple(::OneBased(xs)...); }, x.ref_);
    } else {
      os << ++x.ref_;
      --x.ref_;
    }
    return os;
  }

 private:
  T ref_;
};

template <class T>
OneBased(T&&) -> OneBased<T>;

template <class... Ts>
OneBased(Ts&&...) -> OneBased<std::tuple<Ts...>>;

using namespace std;

// https://github.com/kth-competitive-programming/kactl
namespace kactl {

#define rep(i, a, b) for (int i = a; i < (b); ++i)
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;

const int LIM = 7416256;
vi eratosthenes() {
  const int S = (int)round(sqrt(LIM)), R = LIM / 2;
  vi pr = {2}, sieve(S + 1);
  pr.reserve(int(LIM / log(LIM) * 1.1));
  vector<pii> cp;
  for (int i = 3; i <= S; i += 2)
    if (!sieve[i]) {
      cp.push_back({i, i * i / 2});
      for (int j = i * i; j <= S; j += 2 * i) sieve[j] = 1;
    }
  for (int L = 1; L <= R; L += S) {
    array<bool, S> block{};
    for (auto& [p, idx] : cp)
      for (int i = idx; i < S + L; idx = (i += p)) block[i - L] = 1;
    rep(i, 0, min(S, R - L)) if (!block[i]) pr.push_back((L + i) * 2 + 1);
  }
  return pr;
}

typedef unsigned long long ull;
ull modmul(ull a, ull b, ull M) {
  ll ret = a * b - M * ull(1.L / M * a * b);
  return ret + M * (ret < 0) - M * (ret >= (ll)M);
}
ull modpow(ull b, ull e, ull mod) {
  ull ans = 1;
  for (; e; b = modmul(b, b, mod), e /= 2)
    if (e & 1) ans = modmul(ans, b, mod);
  return ans;
}

bool isPrime(ull n) {
  if (n < 2 || n % 6 % 4 != 1) return (n | 1) == 3;
  ull A[] = {2, 325, 9375, 28178, 450775, 9780504, 1795265022},
      s = __builtin_ctzll(n - 1), d = n >> s;
  for (ull a : A) {
    ull p = modpow(a % n, d, n), i = s;
    while (p != 1 && p != n - 1 && a % n && i--)
      p = modmul(p, p, n);
    if (p != n - 1 && i != s) return 0;
  }
  return 1;
}

#undef rep

}  // namespace kactl

#define IN(...) (cin >> forward_as_tuple(__VA_ARGS__))
#define OUT(...) (cout << forward_as_tuple(__VA_ARGS__) << '\n')

#endif  // __INCLUDE_LEVEL__ == 1