#include <bits/stdc++.h>

using namespace std;

const int OO = 1e9;
const double EPS = 1e-9;

#define ndl cout << '\n'
#define sz(v) int(v.size())
#define pb push_back
#define mp make_pair
#define fs first
#define sc second
#define present(a, x) (a.find(x) != a.end())
#ifdef LOCAL
#define db(...) ({cout << "> Line " << __LINE__  \
		<< ": "; _db(#__VA_ARGS__, __VA_ARGS__);})
#define RNG() rng()
#else
#define db(...) true
#define RNG() true
#endif

template<class T>
void _db(const char *dbStr, T e) {
	cout << dbStr << " = " << e << endl;
}
template<class T, class... L>
void _db(const char *dbStr, T e, L... r) {
  while(*dbStr != ',') cout << *dbStr++;
  cout << " = " << e << ','; _db(dbStr + 1, r...);
}
template<class S, class T>
ostream& operator<<(ostream& o, const map<S, T>& v) {
	o << "["; int i = 0;
	for (const pair<S, T>& pr : v) o << (!i++ ? "" : ", ") << "{"
	<< pr.fs << " : " << pr.sc << "}"; return o << "]";
}
template<template <class, class...> class S, class T, class... L>
ostream& operator<<(ostream& o, const S<T, L...>& v) {
	o << "["; int i = 0;
	for (const auto& e : v) o << (!i++ ? "" : ", ") << e;
	return o << "]";
}
template<class S, class T>
ostream& operator<<(ostream& o, const pair<S, T>& pr) {
	return o << "(" << pr.fs << ", " << pr.sc << ")";
}
ostream& operator<<(ostream& o, const string& s) {
	for (const char& c : s) o << c;
	return o;
}

template<class T> using V = vector<T>;
template<class T> using VV = V<V<T>>;
template<class T> using VVV = VV<V<T>>;
using ll = long long;
using pii = pair<int, int>;
using vi = V<int>;
using vii = V<pii>;
using vvi = VV<int>;
using mii = map<int, int>;
using umii = unordered_map<int, int>;
using si = set<int>;
using usi = unordered_set<int>;

const long long MX_P = 1e18 + 5;
int NN, zeros;
ll K;
V<ll> A, P, N;

bool good(ll mid) {
	ll cnt = 0;

	if (mid >= 0) {
		cnt += zeros * 1LL * (zeros - 1) / 2 + zeros * 1LL * (NN - zeros) + sz(P) * 1LL * sz(N);

		for (int i = 0; i < sz(N); ++i)
			cnt += max(int(upper_bound(N.begin(), N.end(), mid / N[i]) - (N.begin() + i + 1)), 0);

		for (int i = 0; i < sz(P); ++i)
			cnt += max(int(upper_bound(P.begin(), P.end(), mid / P[i]) - (P.begin() + i + 1)), 0);

	} else
		for (int i = 0; i < sz(P); ++i)
			cnt += N.end() - lower_bound(N.begin(), N.end(), (-mid + P[i] - 1) / P[i]);

	return cnt >= K;
}

int main() {
	#ifdef LOCAL
	auto stTime = clock();
	freopen("in.txt", "r", stdin);
	mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
	#endif
	ios::sync_with_stdio(false);
	cout.precision(10);
	cin.tie(0);

	cin >> NN >> K;

	A.assign(NN, 0);


	for (int i = 0; i < NN; ++i)
		cin >> A[i];

	for (int i = 0; i < NN; ++i) {
		zeros += A[i] == 0;
		if (A[i] < 0)
			N.pb(-A[i]);
		else if (A[i] > 0)
			P.pb(A[i]);
	}


	sort(N.begin(), N.end());
	sort(P.begin(), P.end());

	ll lo = -MX_P, hi = MX_P;

	while (hi - lo > 5) {
		ll mid = (lo + hi) / 2;
		if (good(mid))
			hi = mid;
		else
			lo = mid + 1;
	}

	for (ll i = lo; i <= hi; ++i) {
		if (good(i)) {
			cout << i << '\n';
			return 0;
		}
	}



	#ifdef LOCAL
	cout << "\n\n\nExecution time: " <<
		(clock() - stTime) * 1e3 / CLOCKS_PER_SEC << " ms" << endl;
	#endif
    return 0;
}


Measured memory_bytes: 3956