#![allow(unused, non_snake_case, dead_code, non_upper_case_globals)]
use std::cmp::*;
use std::collections::*;
use std::mem::*;
/*
N(N-1)/2 通りのペア
 それぞれのペアについて積を求め、小さい順に並べ替えたとき、K番目にくる数
*/
fn main() {
    let (r, w, e) = (std::io::stdin(), std::io::stdout(), std::io::stderr());
    let mut io = IO::new(r.lock(), w.lock(), e.lock());
    let (N, K) = (io.read::<usize>(), io.read::<usize>());
    let mut A = io.readn::<i64>(N);
    A.sort();
    let poss = A.iter().filter(|&x| x > &0).collect::<Vec<_>>();
    let negs = A.iter().filter(|&x| x < &0).collect::<Vec<_>>();
    let zeros = A.iter().filter(|&x| x == &0).collect::<Vec<_>>();
    let zeroc = zeros.len();
    let mut ok = -999999999999999999i64;
    let mut ng = 999999999999999999i64;
    io.debug(&poss);
    io.debug(&negs);

    while (ok - ng).abs() > 1 {
        let mid = (ok + ng) / 2;

        let mut j = poss.len();
        let mut cnt = 0usize;
        for (i, &x) in A.iter().enumerate() {
            if x >= 0 {
                let mut l = -1 as i64;
                let mut r = N as i64;
                while (r - l).abs() > 1 {
                    let m = (r + l) / 2;
                    if x * A[m as usize] < mid {
                        l = m;
                    } else {
                        r = m;
                    }
                }
                cnt += (l + 1) as usize;
            } else {
                let mut l = -1i64;
                let mut r = N as i64;
                while (r - l).abs() > 1 {
                    let m = (l + r) / 2;
                    if x * A[m as usize] < mid {
                        r = m;
                    } else {
                        l = m;
                    }
                }
                let r = r as usize;
                cnt += (N - r);
            }
            if x * x < mid {
                cnt -= 1;
            }
        }
        // for (i, &x) in poss.iter().enumerate() {
        //     while j > i && poss[j - 1] * x > mid {
        //         j -= 1;
        //     }
        //     if j > i {
        //         cnt += j - i - 1;
        //     }
        // }
        // io.debug2("poss poss", cnt);
        // if mid >= 0 && zeroc >= 1 {
        //     cnt += (zeroc * (zeroc - 1)) / 2 + zeroc * (poss.len() + negs.len());
        // }
        // io.debug2("zero", cnt);
        // let mut j = negs.len();
        // for (i, &x) in poss.iter().enumerate() {
        //     while j > 1 && x * negs[j - 1] > mid {
        //         j -= 1;
        //     }
        //     cnt += j + 1;
        // }
        // io.debug2("pos*neg", cnt);
        // let mut j = negs.len();
        // for (i, &x) in negs.iter().enumerate() {
        //     while j > i && negs[j - 1] * x > mid {
        //         j -= 1;
        //     }
        //     if j > i {
        //         cnt += j - i - 1;
        //     }
        // }
        // io.debug2(mid, cnt);
        cnt /= 2;

        if cnt < K {
            ok = mid;
        } else {
            ng = mid;
        }
    }
    io.writeln(ok);
}

// Ordの型
trait BinarySearch<T> {
    fn lower_bound_by<F: Fn(&T) -> bool>(&self, f: F) -> usize;
    fn lower_bound(&self, x: &T) -> usize;
    fn upper_bound(&self, x: &T) -> usize;
}

impl<T: Ord> BinarySearch<T> for [T] {
    fn lower_bound_by<F: Fn(&T) -> bool>(&self, f: F) -> usize {
        let mut ng = -1;
        let mut ok = self.len() as i64;
        while (ok as i32 - ng as i32).abs() > 1 {
            let mid = (ok + ng) / 2;
            if f(&self[mid as usize]) {
                ok = mid;
            } else {
                ng = mid;
            }
        }
        ok as usize
    }
    fn lower_bound(&self, x: &T) -> usize {
        self.lower_bound_by(|y| y >= x)
    }

    fn upper_bound(&self, x: &T) -> usize {
        self.lower_bound_by(|y| y > x)
    }
}

static MX: usize = 1010101;
static MOD: i64 = 1000000007;
static INF: i64 = std::i64::MAX >> 1;
// IO
use std::io::*;
struct IO<R: Read, W: Write, E: Write> {
    Read: R,
    Write: BufWriter<W>,
    Error: BufWriter<E>,
}
impl<R: Read, W: Write, E: Write> IO<R, W, E> {
    fn new(r: R, w: W, e: E) -> IO<R, W, E> {
        IO {
            Read: r,
            Write: BufWriter::new(w),
            Error: BufWriter::new(e),
        }
    }
    fn read<T>(&mut self) -> T
    where
        T: std::str::FromStr,
    {
        let next: String = self
            .Read
            .by_ref()
            .bytes()
            .map(|c| c.unwrap() as char)
            .skip_while(|c| c.is_whitespace())
            .take_while(|c| !c.is_whitespace())
            .collect();
        next.parse().ok().unwrap()
    }
    fn chars(&mut self) -> Vec<char> {
        self.read::<String>().chars().collect()
    }
    fn chari(&mut self) -> Vec<i64> {
        self.chars()
            .iter()
            .map(|&c| (c as u8 - b'0') as i64)
            .collect::<Vec<i64>>()
    }
    fn readn<T: std::str::FromStr>(&mut self, n: usize) -> Vec<T> {
        (0..n).map(|_| self.read::<T>()).collect::<Vec<_>>()
    }
    fn readmat<T: std::str::FromStr>(&mut self, n: usize, m: usize) -> Vec<Vec<T>> {
        (0..n).map(|_| self.readn(m)).collect()
    }
    fn write<S: ToString>(&mut self, val: S) {
        self.Write.write(val.to_string().as_bytes());
    }
    fn writeln<S: ToString>(&mut self, val: S) {
        self.Write.write(val.to_string().as_bytes());
        self.Write.write(b"\n");
    }
    fn debug<S: std::fmt::Debug>(&mut self, val: S) {
        writeln!(self.Error, "(debug) {:?}", &val);
    }
    fn debug2<S: std::fmt::Debug, T: std::fmt::Debug>(&mut self, val1: S, val2: T) {
        writeln!(self.Error, "(debug2) {:?} -> {:?}", val1, val2);
    }
    fn debug3<S: std::fmt::Debug, T: std::fmt::Debug, U: std::fmt::Debug>(
        &mut self,
        val1: S,
        val2: T,
        val3: U,
    ) {
        writeln!(
            self.Error,
            "(debug3) {:?} -> {:?} -> {:?}",
            val1, val2, val3
        );
    }
}


Measured memory_bytes: 5928