#include <bits/stdc++.h>

int M;
std::vector<std::pair<int, int>> Twins;

void init() {
  const int MX = 10101010;
  bool is_Prime[MX];
  std::fill(is_Prime, is_Prime + MX, true);
  for (int i = 2; i < MX; i++) {
    if (is_Prime[i]) {
      for (int j = i + i; j < MX; j += i) {
        is_Prime[j] = false;
      }
    }
  }
  for (int i = 2; i + 2 < MX; i++) {
    if (is_Prime[i] && is_Prime[i + 2]) {
      Twins.emplace_back(i, i + 2);
    }
  }
  M = Twins.size();
}

void solve() {
  long long n;
  std::cin >> n;
  if (n < 15) {
    std::cout << "-1\n";
  } else {
    int lo = 0, up = M;
    while (up - lo > 1) {
      int mid = (lo + up) / 2;
      auto check = [&](int x) -> bool {
        return 1LL * Twins[x].first * Twins[x].second <= n;
      };
      (check(mid) ? lo : up) = mid;
    }
    std::cout << 1LL * Twins[lo].first * Twins[lo].second << '\n';
  }
}

int main() {
  std::ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  init();
  int t;
  std::cin >> t;
  for (;t--;) {
    solve();
  }
}