#include <bits/stdc++.h>

using namespace std;

int main() {
    const int M = 1e7;
    vector<int> isPrime(M + 1, true);
    isPrime[0] = false, isPrime[1] = false;
    for (int i = 2; i <= M; i++) {
        if (isPrime[i]) {
            for (int j = i + i; j <= M; j += i) {
                isPrime[j] = false;
            }
        }
    }
    vector<int> prime;
    for (int i = 2; i <= M; i++) {
        if (isPrime[i]) prime.push_back(i);
    }
    vector<long long> ans;
    for (int i = 1; i < prime.size(); i++) {
        if (prime[i] - prime[i - 1] == 2) {
            ans.push_back((long long) prime[i - 1] * prime[i]);
        }
    }
    
    int T;
    cin >> T;
    while (T--) {
        long long N;
        cin >> N;
        if (N <= 14) {
            cout << -1 << endl;
        } else {
            cout << *prev(upper_bound(ans.begin(), ans.end(), N)) << endl;
        }
    }
    return 0;
}