#include <bits/stdc++.h>

using namespace std;

void solve() {
    long long N;
    cin >> N;

    if (N < 6) {
        cout << -1 << endl;
        return;
    }

    long long max_p_candidate = (long long)sqrt(N) + 2;
    vector<bool> is_prime(max_p_candidate + 1, true);
    is_prime[0] = is_prime[1] = false;

    for (long long i = 2; i * i <= max_p_candidate; ++i) {
        if (is_prime[i]) {
            for (long long j = i * i; j <= max_p_candidate; j += i) {
                is_prime[j] = false;
            }
        }
    }

    for (long long p = max_p_candidate - 2; p >= 2; --p) {
        if (is_prime[p] && is_prime[p + 2]) {
            long long prod = p * (p + 2);
            if (prod <= N) {
                cout << prod << endl;
                return;
            }
        }
    }

    cout << -1 << endl;
}

int main() {
    int t;
    cin >> t;
    
    while (t--) solve();
    
    return 0;
}