#include <bits/stdc++.h>
using namespace std;

vector<long long> twin_primes;

void sieve_twin_primes(int n) {
    vector<bool> is_prime(n + 1, true);
    is_prime[0] = is_prime[1] = false;
    for (int i = 2; i * i <= n; i++) {
        if (is_prime[i]) {
            for (int j = i * i; j <= n; j += i) {
                is_prime[j] = false;
            }
        }
    }
    for (int i = 2; i + 2 <= n; i++) {
        if (is_prime[i] && is_prime[i + 2]) {
            twin_primes.push_back(i);
        }
    }
}

void solve() {
    long long N;
    cin >> N;
    int ok = -1, ng = twin_primes.size();
    while (abs(ok - ng) > 1) {
        int mid = (ok + ng) / 2;
        if (twin_primes[mid] * (twin_primes[mid] + 2) <= N) {
            ok = mid;
        } else {
            ng = mid;
        }
    }

    if (ok == -1) {
        cout << -1 << endl;
    } else {
        cout << twin_primes[ok] * (twin_primes[ok] + 2) << endl;
    }
}

int main() {
    int T;
    cin >> T;
    sieve_twin_primes((int)1e7);
    while (T--) {
        solve();
    }
}