#define _USE_MATH_DEFINES
#include <iostream>
#include <fstream>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <cassert>
#include <string>
#include <vector>
#include <utility>
#include <complex>
#include <set>
#include <map>
#include <unordered_map>
#include <queue>
#include <stack>
#include <deque>
#include <tuple>
#include <bitset>
#include <limits>
#include <algorithm>
#include <array>
#include <random>
#include <complex>
#include <chrono>
#include <regex>
using namespace std;
typedef long double ld;
typedef long long ll;
typedef vector<int> vint;
typedef vector<ll> vll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<double, double> pdd;
typedef complex<ld> compd;
#define quickIO()	{cin.tie(0);	cout.sync_with_stdio(false);}
#define reach(i,a)	for(auto i:a)
#define rep(i,n)	for(int i=0;i<((int)n);i++)
#define REP(i,n)	for(int i=0;i<=((int)n);i++)
#define srep(i,a,n)	for(int i=a;i<((int)n);i++)
#define SREP(i,a,n)	for(int i=a;i<=((int)n);i++)
#define rrep(i,n)	for(int i=n-1;i>=0;i--)
#define RREP(i,n)	for(int i=n;i>=0;i--)
#define all(a)	(a).begin(),(a).end()
#define mp(a,b)	make_pair(a,b)
#define mt	make_tuple
#define pb	push_back
template<typename T> istream& operator >> (istream& is, vector<T>& vec) {
	for (T& x : vec)	is >> x;
	return is;
}
template<typename T> ostream& operator << (ostream& os, vector<T>& vec) {
	os << "[";
	rep(i, vec.size())	os << (i ? ", " : "") << vec[i];
	os << "]";
	return os;
}
template<typename T> istream& operator >> (istream& is, pair<T, T>& p) {
	is >> p.first >> p.second;
	return is;
}
template<typename T> ostream& operator << (ostream& os, pair<T, T>& p) {
	os << p.first << " " << p.second;
	return os;
}
template<typename T> bool operator < (vector<T>& a, vector<T>& b) {
	rep(i, a.size()) {
		if (i == b.size())	return false;
		if (a[i] < b[i])	return true;
		else if (a[i] > b[i])	return false;
	}
	return false;
}
template<typename T> bool operator > (vector<T>& a, vector<T>& b) {
	rep(i, a.size()) {
		if (i == b.size())	return true;
		if (a[i] < b[i])	return false;
		else if (a[i] > b[i])	return true;
	}
	return false;
}
int bitcnt(ll x) {
	x = ((x & 0xAAAAAAAAAAAAAAAA) >> 1) + (x & 0x5555555555555555);
	x = ((x & 0xCCCCCCCCCCCCCCCC) >> 2) + (x & 0x3333333333333333);
	x = ((x & 0xF0F0F0F0F0F0F0F0) >> 4) + (x & 0x0F0F0F0F0F0F0F0F);
	x = ((x & 0xFF00FF00FF00FF00) >> 8) + (x & 0x00FF00FF00FF00FF);
	x = ((x & 0xFFFF0000FFFF0000) >> 16) + (x & 0x0000FFFF0000FFFF);
	x = ((x & 0xFFFFFFFF00000000) >> 32) + (x & 0x00000000FFFFFFFF);
	return x;
}
int bitcnt(int x) {
	x = ((x & 0xAAAAAAAA) >> 1) + (x & 0x55555555);
	x = ((x & 0xCCCCCCCC) >> 2) + (x & 0x33333333);
	x = ((x & 0xF0F0F0F0) >> 4) + (x & 0x0F0F0F0F);
	x = ((x & 0xFF00FF00) >> 8) + (x & 0x00FF00FF);
	x = ((x & 0xFFFF0000) >> 16) + (x & 0x0000FFFF);
	return x;
}
ll sqrtll(ll x) {
	ll left = 0, right = x;
	rep(i, 100) {
		ll mid = (left + right) >> 1;
		if (mid * mid <= x)	left = mid;
		else	right = mid;
	}
	return left;
}
ll gcd(ll a, ll b) {
	return b == 0 ? a : gcd(b, a % b);
}
class TimeWatcher
{
	chrono::system_clock::time_point start;

public:
	void start_clock()
	{
		start = chrono::system_clock::now();
	}
	int check()
	{
		auto end = chrono::system_clock::now();
		return chrono::duration_cast<chrono::milliseconds>(end - start).count();
	}
} timer;
class RandomMaker
{
public:
	random_device rnd;
	mt19937 mt;

	void setup()
	{
		mt.seed(rnd());
	}
	int rand()
	{
		return mt();
	}
	int rand(int a, int b)
	{
		uniform_int_distribution<> r(a, b);
		return r(mt);
	}
} rnd;

void init()
{
	timer.start_clock();
	rnd.setup();
}
#define debug(x)	printf("Case #%d: ", x)
#define DEBUG 0
const ld infl = 1e100;
const ll mod = 998244353;
const double eps = 1e-15;
const ll inf = 1e15;
const int dx[] = { 1,0,-1,0,0 };
const int dy[] = { 0,1,0,-1,0 };

bool check(ll k, ll mid, vll& pos, vll& neg, ll zero) {
	ll cnt = 0;	// mid以下の組み合わせ数
	if (mid >= 0) {
		// 積<=0は無条件にcntに加えて良い
		cnt += zero * (zero - 1) / 2 + zero * (pos.size() + neg.size());
		cnt += pos.size() * neg.size();
		// 積>0になるのはpos*posとneg*negのみ
		int idx = pos.size() - 1;
		rep(j, pos.size()) {
			while (idx > j&& pos[idx] * pos[j] > mid)	idx--;
			cnt += max(0, idx - j);
		}
		idx = neg.size() - 1;
		rep(j, neg.size()) {
			while (idx > j&& neg[idx] * neg[j] > mid)	idx--;
			cnt += max(0, idx - j);
		}
	}
	else {
		// 積>=0は無条件にカウントしない
		// 積<0はneg*posのみ
		int idx = 0;
		rep(j, neg.size()) {
			while (idx < pos.size() && neg[j] * pos[pos.size() - 1 - idx] >= -mid) idx++;
			cnt += idx;
		}
	}
	return cnt >= k;
}

int main() {
	ll n, k;	cin >> n >> k;
	vll a(n);	cin >> a;
	vll pos, neg;
	ll zero = 0;
	rep(i, n) {
		if (a[i] > 0)	pos.push_back(a[i]);
		else if (a[i] < 0)	neg.push_back(-a[i]);
		else	zero++;
	}
	sort(all(pos));	sort(all(neg));
	ll left = -1e18;
	ll right = 1e18 + 1;
	rep(i, 100) {
		ll mid = (left + right) / 2;
		if (check(k, mid, pos, neg, zero))	right = mid;
		else	left = mid;
	}
	for (ll i = left; i <= right; i++) {
		if (check(k, i, pos, neg, zero)) {
			cout << i << endl;
			return 0;
		}
	}
}

Measured memory_bytes: 3956