#include <bits/stdc++.h>
using namespace std;

using ll = long long;
#define int ll

// [a -> b-1]
#define reps(i, a, b) for (int i = (int)(a); i < (int)(b); i++)
// [0 -> a-1]
#define rep(i, a) reps(i, 0, (a))
// [a-1 -> b]
#define rreps(i, a, b) for (int i = (int)((a)-1); i >= (int)(b); i--)
// [a-1 -> 0]
#define rrep(i, a) rreps(i, a, 0)
#define all(v) (v).begin(), (v).end()
// next_permutation(all(v))
#define PERM(v) next_permutation(all(v))
/*sort(all(v));
 * (v).erase(unique(all(v)), v.end())*/
#define UNIQUE(v)\
	sort(all(v));\
	(v).erase(unique(all(v)), v.end())
// b is [a, c)
#define RANGE(a, b, c) ((a) <= (b) && (b) < (c))
// c is [a, e) && d is [b, f)
#define RANGE2D(a, b, c, d, e, f) (RANGE((a), (c), (e)) && RANGE((b), (d), (f)))
#define chmin(a, b) a = min(a, (b))
#define chmax(a, b) a = max(a, (b))
#define fcout cout << fixed << setprecision(15)
#define YES(f) cout << ((f) ? YES_STR : NO_STR) << endl;

#ifdef LOCAL_DEBUG_OPTION
namespace debug_print_n{
struct DebugPrint {
	template<class T, class U = remove_const_t<remove_reference_t<T>>>
	static enable_if_t<is_integral<U>::value && !is_same<U, bool>::value && !is_same<U, char>::value> DUMP_SUB_FUNCTION(T x) {
		cerr << x;
	}
	template<class T, class U = remove_const_t<remove_reference_t<T>>>
	static enable_if_t<is_same<U, bool>::value> DUMP_SUB_FUNCTION(T x) {
		if (x) cerr << "True";
		else cerr << "False";
	}
	template<class T, class U = remove_const_t<remove_reference_t<T>>>
	static enable_if_t<is_same<U, char>::value> DUMP_SUB_FUNCTION(T x) {
		cerr << '\'' << x << '\'';
	}
	template<class T, class U = remove_const_t<remove_reference_t<T>>>
	static enable_if_t<is_same<U, string>::value> DUMP_SUB_FUNCTION(T x) {
		cerr << '\"' << x << '\"';
	}
	template<class T>
	static enable_if_t<is_same<T, const char*>::value> DUMP_SUB_FUNCTION(T x) {
		cerr << string(x);
	}
	template<class T>
	static enable_if_t<true> DUMP_SUB_FUNCTION(vector<T> x) {
		cerr << '{';
		for (size_t i = 0; i < x.size(); i++) {
			if (i) cerr << ", ";
			DUMP_SUB_FUNCTION(x[i]);
		}
		cerr << '}';
	}
	template<class T, size_t N>
	static enable_if_t<true> DUMP_SUB_FUNCTION(array<T, N> x) {
		cerr << '{';
		for (size_t i = 0; i < x.size(); i++) {
			if (i) cerr << ", ";
			DUMP_SUB_FUNCTION(x[i]);
		}
		cerr << '}';
	}
	template<class T>
	static enable_if_t<true> DUMP_SUB_FUNCTION(set<T> x) {
		cerr << '[';
		size_t i = 0;
		for (auto itr = x.begin(); itr != x.end(); itr++, i++) {
			if (i) cerr << ", ";
			DUMP_SUB_FUNCTION(*itr);
		}
		cerr << ']';
	}
	template<class T, class U>
	static enable_if_t<true> DUMP_SUB_FUNCTION(map<T, U> x) {
		cerr << '[';
		size_t i = 0;
		for (auto itr = x.begin(); itr != x.end(); itr++, i++) {
			if (i) cerr << ", ";
			DUMP_SUB_FUNCTION(itr->first);
			cerr << " : ";
			DUMP_SUB_FUNCTION(itr->second);
		}
		cerr << ']';
	}
	template<class T, class U = remove_const_t<remove_reference_t<T>>>
	static enable_if_t<is_floating_point<U>::value> DUMP_SUB_FUNCTION(T x) {
		cerr << fixed << setprecision(5) << x;
	}
	template<class T, class U>
	static enable_if_t<true> DUMP_SUB_FUNCTION(pair<T, U> p) {
		cerr << '(';
		DUMP_SUB_FUNCTION(p.first);
		cerr << ", ";
		DUMP_SUB_FUNCTION(p.second);
		cerr << ')';
	}
	template<int num = 0, class... Args>
	static enable_if_t<num == sizeof...(Args)> DUMP_SUB_FUNCTION(tuple<Args...> t) {
		if (num) cerr << ')';
	}
	template<int num = 0, class... Args>
	static enable_if_t<num < sizeof...(Args)> DUMP_SUB_FUNCTION(tuple<Args...> t) {
		if (num == 0) cerr << '(';
		DUMP_SUB_FUNCTION(get<num>(t));
		if (num + 1 < sizeof...(Args)) cerr << ", ";
		DUMP_SUB_FUNCTION<num+1>(t);
	}
	template<long unsigned N>
	static enable_if_t<true> DUMP_SUB_FUNCTION(bitset<N> x) {
		cerr << x;
	}
};
void dump() {
	cerr << endl;
}
template<class Head, class... Tail>
void dump(Head&& head, Tail&&... tail) {
	DebugPrint::DUMP_SUB_FUNCTION(head);
	if (sizeof...(Tail) != 0) {
		cerr << ' ';
	}
	dump(forward<Tail>(tail)...);
}
} // namespace debug_print_n
using debug_print_n::dump;
#else
template<class... Args> void dump(Args&&... args) { }
#endif

// meguru<T>(ok, ng, isok)で呼ぶ
template<class T>
T meguru(T ok, T ng, function<bool(T)> isok) {
	while (abs(ok - ng) > 1) {
		T mid = (ok + ng) / 2;
		(isok(mid) ? ok : ng) = mid;
	}
	return ok;
}

signed main(){
	int N, K; cin >> N >> K;
	vector<int> P, M;
	int z = 0;
	rep(i, N) {
		int x; cin >> x;
		if (x > 0) P.push_back(x);
		else if (x < 0) M.push_back(-x);
		else z++;
	}
	int p = P.size();
	int m = M.size();
	int mc = p * m;
	int zc = z * (p + m);
	zc += z * (z-1) / 2;
	int pc = N * (N - 1) / 2 - mc - zc;
	if (K <= mc) {
		sort(all(P));
		sort(all(M));
		auto cnt = [&](int mid) -> int {
			int r = 0;
			rep(i, P.size()) {
				// r += M.end() - lower_bound(all(M), (mid + P[i] - 1) / P[i]);
				r += M.end() - partition_point(all(M), [&](auto x) {
					return x * P[i] < mid;
				});
			}
			return r;
		};
		cout << -meguru<int>(1, 2e18+100, [&](int mid) {
			return cnt(mid) >= K;
		}) << endl;
	} else if (K <= mc + zc) {
		cout << 0 << endl;
	} else {
		sort(all(P));
		sort(all(M));
		auto cnt = [](int mid, const vector<int>& v) -> int {
			int r = 0;
			rep(i, v.size()) {
				r += v.end() - lower_bound(v.begin()+i+1, v.end(), (mid + v[i] - 1) / v[i]);
			}
			return r;
		};
		cout << meguru<int>(1, 2e18+100, [&](int mid) {
			int c = cnt(mid, P) + cnt(mid, M);
			return c >= N * (N-1) / 2 - K + 1;
		}) << endl;
	}
	return 0;
}


Measured memory_bytes: 2420