#include <iostream>
#include <vector>
#include <cmath>
#include <algorithm>

using namespace std;
using ll = long long;

const ll MAX = 1e7;
vector<bool> sieve(MAX + 1, true);
vector<ll> L;

int main() {
    sieve[0] = sieve[1] = false;
    for (ll i = 2; i <= sqrt(MAX); ++i) {
        if (sieve[i]) {
            for (ll j = i * i; j <= MAX; j += i) {
                sieve[j] = false;
            }
        }
    }

    // Lを作る: 素数pで、p+2も素数であるものを保存
    for (ll i = 2; i <= MAX - 2; ++i) {
        if (sieve[i] && sieve[i + 2]) {
            L.push_back(i);
        }
    }

    ll T;
    cin >> T;
    while (T--) {
        ll N;
        cin >> N;
        ll rootN = sqrt(N);
        auto it = upper_bound(L.begin(), L.end(), rootN);
        if (it != L.begin()) --it;  // upper_boundなので一つ前に戻す
        while (it != L.begin() && (*it) * (*it + 2) > N) {
            --it;
        }
        if ((*it) * (*it + 2) > N) {
            cout << -1 << endl;
        } else {
            cout << (*it) * (*it + 2) << endl;
        }
    }

    return 0;
}