fn main() {
    input!{
		t: usize,
	}

	// 素数リスト
	let primes = prime_list(10_000_000);

	// p,p+2を満たすpだけを列挙する
	let pprimes = match_primes(&primes);

	for _ in 0..t {
		input!{
			n: usize,
		}

		// 二分探索で条件を満たすp番目のmaxを調べる
		let p = get_idx(&pprimes, n);

		if p != INF {
			println!("{}", pprimes[p] * (pprimes[p] + 2));
		}
		else {
			println!("-1");
		}
	}
}

// エラトステネスの篩による素数リスト
pub fn prime_list(x: usize) -> Vec<usize> {
	let mut bools = vec![true; x + 1];
	bools[0] = false;
	bools[1] = false;
	let mut i = 2;
	while i * i <= x {
		if bools[i] {
			let mut now = 2 * i;
			while now <= x {
				bools[now] = false;
				now += i;
			}
		}
		i += 1;
	}
	let mut ret = Vec::new();
	for i in 0..=x {
		if bools[i] {
			ret.push(i)
		};
	}
	ret
}

fn match_primes(primes: &Vec<usize>) -> Vec<usize> {
	let sz = primes.len();
	let mut ret = Vec::new();
	for i in 0..sz-1 {
		if primes[i+1] - primes[i] == 2 {
			ret.push(primes[i]);
		}
	}
	ret
}

fn get_idx(pprimes: &Vec<usize>, n: usize) -> usize {
	// 二分探索で条件を満たすp番目のmaxを調べる
	let mut ok = -1;
	let mut ng = pprimes.len() as i32;
	for _ in 0..50 {
		let mid = ((ok + ng) / 2) as usize;
		if pprimes[mid] * (pprimes[mid] + 2) <= n {
			ok = mid as i32;
		}
		else {
			ng = mid as i32;
		}
	}
	if ok == -1 {
		return INF;
	}
	ok as usize
}

// const MOD17: usize = 1000000007;
// const MOD93: usize = 998244353;
const INF: usize = 1 << 60;
// let dx = vec![!0, 0, 1, 0]; // 上左下右
// let dy = vec![0, !0, 0, 1]; // 上左下右
// let d = vec!{(!0, 0), (0, !0), (1, 0), (0, 1)}; // 上左下右

#[allow(unused)]
use proconio::{input, marker::Chars, marker::Usize1};

#[allow(unused)]
use std::{
	mem::swap,
	cmp::min, cmp::max,
	cmp::Reverse,
	collections::HashSet, collections::BTreeSet,
	collections::HashMap, collections::BTreeMap,
	collections::BinaryHeap,
	collections::VecDeque,
	iter::FromIterator,
};
// 配列のスペース区切り出力
#[allow(unused)]
fn vec_print<T: std::fmt::Display>(vec: &Vec<T>) {
	let sz = vec.len();
	for i in 0..sz-1 {
		print!("{} ", vec[i]);
	}
	println!("{}", vec[sz-1]);
}