#include "bits/stdc++.h"
using namespace std;
#define Rep(i,n) for(int i=0;i<(int)(n);i++)
#define For(i,n1,n2) for(int i=(int)(n1);i<(int)(n2);i++)
#define REP(i,n) for(ll i=0;i<(ll)(n);i++)
#define RREP(i,n) for(ll i=((ll)(n)-1);i>=0;i--)
#define FOR(i,n1,n2) for(ll i=(ll)(n1);i<(ll)(n2);i++)
#define RFOR(i,n1,n2) for(ll i=((ll)(n1)-1);i>=(ll)(n2);i--)
#define all(a)  (a).begin(),(a).end()
#define SORT(a) sort((a).begin(),(a).end())
#define oorret 0
#define oor(x) [&](){try{x;} catch(const out_of_range& oor){return oorret;} return x;}()
#define IOS cin.tie(0),ios::sync_with_stdio(false)
typedef long long ll;
typedef unsigned long long ull;
typedef std::pair<ll, ll> P;
template<typename T1, typename T2> inline bool chmin(T1& a, T2 b) { if (a > b) { a = b; return 1; }return 0; }
template<typename T1, typename T2> inline bool chmax(T1& a, T2 b) { if (a < b) { a = b; return 1; }return 0; }
template<class Type>struct is_vector : std::false_type {};
template<class ValueType, class Alloc>struct is_vector<std::vector<ValueType, Alloc>> : std::true_type {};
template <typename T> inline std::ostream& operator << (std::ostream& out, const std::vector<T>& v) {
	if (v.empty())return out;
	constexpr bool is_vector_v = is_vector<T>::value;
	if (is_vector_v)for (auto itr = v.begin(); itr != v.end();)out << (*itr), out << ((++itr != v.end()) ? "\n" : "");
	else for (auto itr = v.begin(); itr != v.end();)out << (*itr), out << ((++itr != v.end()) ? " " : "");
	return out;
}
inline void put() {}
template<class T> inline void put(const T& first) { std::cout << first << "\n"; }
template<class T, class... N> inline void put(const T& first, const N& ... rest) { std::cout << first << " "; put(rest...); }
inline void putn() {}
template<class T, class... N> inline void putn(const T& first, const N& ... rest) { std::cout << first << "\n"; putn(rest...); }

int main() {
	IOS;
	ll n, k;
	cin >> n >> k;
	vector<ll> a(n);
	vector<ll> m, z, p;
	REP(i, n) {
		cin >> a[i];
		if (a[i] < 0) {
			m.push_back(-a[i]);
		} else if (a[i] > 0) {
			p.push_back(a[i]);
		} else {
			z.push_back(a[i]);
		}
	}
	ll mc = m.size(), zc = z.size(), pc = p.size();
	sort(all(a));
	sort(all(m));
	sort(all(p));
	ll lb = -2e18, ub = 2e18;
	while (ub - lb > 1) {
		ll mid = (ub + lb) / 2;
		ll tmp = 0;
		/*REP(i, n) {
			ll k1 = (mid + a[i] - 1) / a[i] - 1;
			auto itr = upper_bound(all(a), k1) - a.begin();
			tmp += itr;
			if (a[i] * a[i] < mid) {
				tmp--;
			}
		}*/
		if (mid > 0) {
			tmp += zc * (n - zc) + zc * (zc - 1) / 2 + mc * pc;
			ll tmp2 = 0;
			REP(i, n) {
				if (a[i] > 0) {
					ll k1 = (abs(mid) + a[i] - 1) / a[i] - 1;
					auto itr = upper_bound(all(p), k1) - p.begin();
					tmp2 += itr;
					if (a[i] * a[i] < mid) {
						tmp2--;
					}
				} else if (a[i] < 0) {
					ll t = abs(a[i]);
					ll k1 = (abs(mid) + t - 1) / t - 1;
					auto itr = upper_bound(all(m), k1) - m.begin();
					tmp2 += itr;
					if (t * t < mid) {
						tmp2--;
					}
				}
			}
			tmp += tmp2 / 2;
		} else if (mid == 0) {
			tmp += mc * pc;
		} else {
			REP(i, n) {
				if (a[i] > 0) {
					ll k1 = (abs(mid) + a[i] - 1) / a[i] - 1;
					auto itr = upper_bound(all(m), k1) - m.begin();
					tmp += m.size()-itr;
				}
				if (a[i] < 0) {
					ll t = abs(a[i]);
					ll k1 = (abs(mid) + t - 1) / t - 1;
					auto itr = upper_bound(all(p), k1) - p.begin();
					tmp += p.size()-itr;
				}
			}
			tmp /= 2;
		}
		// tmp = n * (n - 1) / 2 - tmp;
		if (tmp < k) {
			lb = mid;
		} else {
			ub = mid;
		}
	}
	if (lb < 0) {
		put(lb + 1);
		return 0;
	}
	put(lb);
	return 0;
}

Measured memory_bytes: 4084