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

using i32 = int;
using i64 = long long;
using i128 = __int128_t;
using f64 = double;
using p2 = pair<i64, i64>;
using p3 = tuple<i64, i64, i64>;
using mint = atcoder::modint998244353;

void _main();
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(18);
  _main();
}

void _main() {
  i64 l, r;
  cin >> l >> r;
  r++;
  vector<bool> isprime(30000000, true);
  isprime[0] = isprime[1] = false;
  vector<i32> prime;
  for (i32 i = 2; i < isprime.size(); i++) {
    if (!isprime[i]) continue;
    prime.push_back(i);
    for (i32 j = i + i; j < isprime.size(); j += i) {
      isprime[j] = false;
    }
  }
  for (i64 i = l; i < r; i++) {
    if (i % 45 != 0 || i == 45) continue;
    i64 x = i / 45;
    if (x % 2 == 0 || x % 3 == 0 || x % 5 == 0) continue;
    bool ok = true;
    for (i32 p : prime) {
      if (p <= 5) continue;
      if (p * p > x) break;
      ok &= x % p != 0;
    }
    if (ok) {
      cout << i << "\n";
      return;
    }
  }
  for (i64 i = l; i < r; i++) {
    if (i % 2 == 0) continue;
    i64 x = i;
    i64 a = -1, b = -1, c = -1;
    bool ok = true;
    for (i64 p : prime) {
      if (p * p > x) break;
      if (x % p != 0) continue;
      if (x % (p * p) == 0) {
        ok &= a == -1 && x % (p * p * p) != 0;
        a = p;
        x /= a * a;
        continue;
      }
      ok &= a != -1;
      if (b == -1) {
        b = p;
        x /= b;
      } else {
        ok &= p == x;
        c = x;
        x /= c;
      }
    }
    c = x;
    if (a == -1 || b == -1 || c == -1 || !ok || c == 1) continue;
    assert(a < b && b < c);
    cout << i << "\n";
    return;
  }
  cout << "-1\n";
}