#![allow(unused_imports)]
#![allow(non_snake_case)]
use std::cmp::*;
use std::collections::*;
use std::io::Write;

#[allow(unused_macros)]
macro_rules! debug {
    ($($e:expr),*) => {
        #[cfg(debug_assertions)]
        $({
            let (e, mut err) = (stringify!($e), std::io::stderr());
            writeln!(err, "{} = {:?}", e, $e).unwrap()
        })*
    };
}

#[derive(PartialEq, PartialOrd)]
pub struct Total<T>(pub T);

impl<T: PartialEq> Eq for Total<T> {}

impl<T: PartialOrd> Ord for Total<T> {
    fn cmp(&self, other: &Total<T>) -> std::cmp::Ordering {
        self.0.partial_cmp(&other.0).unwrap()
    }
}

fn main() {
    let v = read_vec::<i64>();
    let (n, k) = (v[0] as usize, v[1]);
    let mut a = read_vec::<i64>();
    a.sort();
    let mut neg_nums = vec![]; // < 0
    let mut pos_nums = vec![]; // > 0

    for &num in a.iter() {
        if num > 0 {
            pos_nums.push(num);
        } else if num < 0 {
            neg_nums.push(num);
        }
    }

    let total_neg_pairs = pos_nums.len() as i64 * neg_nums.len() as i64;

    let mut neg_nums = neg_nums.iter().map(|&x| -x).collect::<Vec<_>>();
    neg_nums.sort();

    let mut a_abs = a.iter().cloned().map(|x| x.abs()).collect::<Vec<_>>();
    a_abs.sort();
    a_abs.reverse();
    let max_abs = a_abs[0] * a_abs[1];

    let mut ans = 0i64;
    if k <= total_neg_pairs {
        // answer is negative
        let criterion = |mid: i64| {
            let mut count = 0i64;
            for &pos_num in pos_nums.iter() {
                let search = (neg_nums.len()
                    - neg_nums.lower_bound(&((mid + pos_num - 1) / pos_num)))
                    as i64;
                count += search;
            }
            count >= k
        };
        let (ok, ng) = binary_search(0, max_abs + 1, criterion);
        ans = -ok;
    } else {
        let zero_count = n - pos_nums.len() - neg_nums.len();
        let k = k
            - zero_count as i64 * (n - zero_count) as i64
            - total_neg_pairs
            - zero_count as i64 * (zero_count as i64 - 1) / 2;
        if k < 0 {
            println!("{}", 0);
            return;
        }

        let criterion = |mid: i64| {
            let mut count = 0i64;

            for (i, &num) in pos_nums.iter().enumerate() {
                let mut search = pos_nums.lower_bound(&((mid + num - 1) / num)) as i64;
                search = max(0, search - i as i64 - 1);
                count += search;
            }
            for (i, &num) in neg_nums.iter().enumerate() {
                let mut search = neg_nums.lower_bound(&((mid + num - 1) / num)) as i64;
                search = max(0, search - i as i64 - 1);
                count += search;
            }
            count < k
        };
        let (ok, ng) = binary_search(0, max_abs + 1, criterion);
        ans = ok;
    }
    println!("{}", ans);
}

fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>()
        .split_whitespace()
        .map(|e| e.parse().ok().unwrap())
        .collect()
}

use std::cmp::Ordering;

pub trait BinarySearch<T> {
    fn lower_bound(&self, x: &T) -> usize;
    fn upper_bound(&self, x: &T) -> usize;
}

impl<T: Ord> BinarySearch<T> for [T] {
    fn lower_bound(&self, x: &T) -> usize {
        let mut low = 0;
        let mut high = self.len();

        while low != high {
            let mid = (low + high) / 2;
            match self[mid].cmp(x) {
                Ordering::Less => {
                    low = mid + 1;
                }
                Ordering::Equal | Ordering::Greater => {
                    high = mid;
                }
            }
        }
        low
    }

    fn upper_bound(&self, x: &T) -> usize {
        let mut low = 0;
        let mut high = self.len();

        while low != high {
            let mid = (low + high) / 2;
            match self[mid].cmp(x) {
                Ordering::Less | Ordering::Equal => {
                    low = mid + 1;
                }
                Ordering::Greater => {
                    high = mid;
                }
            }
        }
        low
    }
}

fn binary_search<F>(lb: i64, ub: i64, criterion: F) -> (i64, i64)
where
    F: Fn(i64) -> bool,
{
    let mut ok = lb;
    let mut ng = ub;
    while ng - ok > 1 {
        let mid = (ng + ok) / 2;
        if criterion(mid) {
            ok = mid;
        } else {
            ng = mid;
        }
    }
    (ok, ng)
}


Measured memory_bytes: 12400