#include <bits/stdc++.h>

using namespace std;

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

    if (N < 15) {
        cout << -1 << endl;
        return;
    }

    long long p_max = (long long)(sqrt(N + 1)) - 1;
    if (p_max < 2) {
        cout << -1 << endl;
        return;
    }

    long long max_limit = p_max + 2;
    vector<bool> is_prime(max_limit + 1, true);
    is_prime[0] = is_prime[1] = false;
    for (long long i = 2; i * i <= max_limit; ++i) {
        if (is_prime[i]) {
            for (long long j = i * i; j <= max_limit; j += i) {
                is_prime[j] = false;
            }
        }
    }

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

    cout << -1 << endl;
}

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