#include <bits/stdc++.h>
//#include <atcoder/all>
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n) - 1; i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r) - 1;i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
std::vector<long long> sieveOfEratosthenes(long long  n = 1000000) {
	std::vector<bool>p(n + 1, true);
	std::vector<long long>ret;
	p[0] = false;
	p[1] = false;
	for (int i = 2; i <= n; ++i) {
		if (!p[i]) continue;
		ret.push_back(i);
		for (int j = 2 * i; j <= n; j += i) p[j] = false;
	}
	return ret;
}
template <class T, class F>
T binarySearch(T ok, T ng, const F &f) {
	while (abs(ok - ng) > 1) {
		T mid = (ok + ng) / 2;
		(f(mid) ? ok : ng) = mid;
	}
	return ok;
}
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	auto ps = sieveOfEratosthenes(10000007);
	vector<long long>x;
	rep(i, ps.size() - 1) {
		if (ps[i] + 2 == ps[i + 1])x.push_back(ps[i]);
	}
	int t; cin >> t;
	while (t--) {
		long long n; cin >> n;
		if (n < 15) {
			cout << -1 << endl;
			continue;
		}
		auto f = [&](const long long tar)->bool {
			return x[tar] * (x[tar] + 2) <= n;
		};
		auto ans = binarySearch<long long>(-1, x.size(), f);
		ans = x[ans] * (x[ans] + 2);
		cout << ans << endl;
	}
	return 0;
}