#include <bits/stdc++.h>
#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,fma")
#pragma GCC optimize("unroll-loops")
using namespace std;
long long MOD = 998244353;
double eps = 1e-12;
void solve() {
  int p, y;
  cin >> p >> y;
  if (p == y) {
    cout << -1;
    return;
  }
  if (y == 3 && p == 2) {
    cout << -1;
    return;
  }
  int j = 0, t = 0;
  for (int i = y; i > p; i--) {
    for (j = 2; j * j <= i; j++) {
      if (i % j == 0) {
        if (j <= p)
          break;
        else
          cout << i;
        return;
      }
    }
    if (j * j > i) {
      cout << i;
      return;
    }
  }
  cout << -1;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  solve();
  return 0;
}
