#include <bits/stdc++.h>
#include <algorithm>
#include <atcoder/all>
using namespace std;
using ll = long long;
#define rep(i, s, t) for (ll i = s; i < (ll)(t); i++)
#define all(x) begin(x), end(x)

template <typename T> bool chmin(T& x, T y) {
	return x > y ? (x = y, true) : false;
}
template <typename T> bool chmax(T& x, T y) {
	return x < y ? (x = y, true) : false;
}

struct IOST {
	IOST() {
		ios::sync_with_stdio(false);
		cin.tie(nullptr);
		cout << fixed << setprecision(20);
	}
} IOST;

vector<ll> dualp;
void setup() {
	int n = 1e7;
	vector<int> mm(n, 0);
	vector<ll> prime;
	rep(i, 2, n) {
		if (mm[i]) continue;
		for (int j = i * 2; j < n; j += i) mm[j] = 1;
		prime.push_back(i);
	}
	int m = prime.size();
	rep(i, 0, m - 1) if (prime[i] + 2 == prime[i + 1])
		dualp.push_back(prime[i] * prime[i + 1]);
	dualp.push_back(1e18);
}

void solve() {
	ll n;
	cin >> n;
	auto itr = upper_bound(dualp.begin(), dualp.end(), n);
	if (itr == dualp.begin()) cout << "-1\n";
	else cout << *(--itr) << "\n";
}

int main() {
	setup();
	int t = 1;
	cin >> t;
	rep(i, 0, t) solve();
}