/* 
 *      Author:    srtry
 *      Created:   2025-04-30T04:38:41+09:00
 */

use proconio::input;

fn solve(&n:&usize, twin_primes_prod:&Vec<usize>) {
    let mut left:usize = 0;
    let mut right:usize = twin_primes_prod.len()-1;
    let mut mid:usize = (left+right+1)/2;
    loop {
        if right-left <= 1 {
            break;
        }
        mid = (left+right+1)/2;
        if twin_primes_prod[mid] <= n {
            left = mid;
        } else {
            right = mid-1;
        }
    }

    if twin_primes_prod[right] <= n {
        println!("{}", twin_primes_prod[right]);
    } else if twin_primes_prod[left] <= n {
        println!("{}", twin_primes_prod[left]);
    } else {
        println!("-1");
    }
}

fn main() {
    input!{
        t:usize,
        case:[usize;t]
    }

    let max_max_p:usize = (*case.iter().max().unwrap() as f64).sqrt() as usize;

    // エラトステネスの篩
    let mut is_prime:Vec<bool> = vec![true;max_max_p+3];
    is_prime[0] = false;
    is_prime[1] = false;
    for i in 2..is_prime.len() {
        if is_prime[i] {
            for j in i..=(max_max_p/i) {
                is_prime[j*i] = false;
            }
        }
    }

    // 双子素数の積
    let mut twin_primes_prod:Vec<usize> = Vec::new();
    for i in 0..=max_max_p {
        if is_prime[i] && is_prime[i+2] {
            twin_primes_prod.push(i*(i+2));
        }
    }

    for c in case.iter() {

        solve(&c, &twin_primes_prod);
    }
}