#include <bits/stdc++.h>
using namespace std;
using lint = long long int;
using pint = pair<int, int>;
using plint = pair<lint, lint>;
struct fast_ios { fast_ios(){ cin.tie(0); ios::sync_with_stdio(false); cout << fixed << setprecision(20); }; } fast_ios_;
#define ALL(x) (x).begin(), (x).end()
#define SZ(x) ((lint)(x).size())
#define POW2(n) (1LL << (n))
#define FOR(i, begin, end) for(int i=(begin),i##_end_=(end);i<i##_end_;i++)
#define IFOR(i, begin, end) for(int i=(end)-1,i##_begin_=(begin);i>=i##_begin_;i--)
#define REP(i, n) FOR(i,0,n)
#define IREP(i, n) IFOR(i,0,n)
template<typename T> istream &operator>>(istream &is, vector<T> &vec){ for (auto &v : vec) is >> v; return is; }
template<typename T> ostream &operator<<(ostream &os, const vector<T> &vec){ os << "["; for (auto v : vec) os << v << ","; os << "]"; return os; }
template<typename T> ostream &operator<<(ostream &os, const deque<T> &vec){ os << "deq["; for (auto v : vec) os << v << ","; os << "]"; return os; }
template<typename T> ostream &operator<<(ostream &os, const set<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream &operator<<(ostream &os, const unordered_set<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream &operator<<(ostream &os, const multiset<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T> ostream &operator<<(ostream &os, const unordered_multiset<T> &vec){ os << "{"; for (auto v : vec) os << v << ","; os << "}"; return os; }
template<typename T1, typename T2> ostream &operator<<(ostream &os, const pair<T1, T2> &pa){ os << "(" << pa.first << "," << pa.second << ")"; return os; }
template<typename TK, typename TV> ostream &operator<<(ostream &os, const map<TK, TV> &mp){ os << "{"; for (auto v : mp) os << v.first << "=>" << v.second << ","; os << "}"; return os; }
template<typename TK, typename TV> ostream &operator<<(ostream &os, const unordered_map<TK, TV> &mp){ os << "{"; for (auto v : mp) os << v.first << "=>" << v.second << ","; os << "}"; return os; }
template<typename T> void ndarray(vector<T> &vec, int len) { vec.resize(len); }
template<typename T, typename... Args> void ndarray(vector<T> &vec, int len, Args... args) { vec.resize(len); for (auto &v : vec) ndarray(v, args...); }
template<typename T> bool mmax(T &m, const T q) { if (m < q) {m = q; return true;} else return false; }
template<typename T> bool mmin(T &m, const T q) { if (q < m) {m = q; return true;} else return false; }
template<typename T1, typename T2> pair<T1, T2> operator+(const pair<T1, T2> &l, const pair<T1, T2> &r) { return make_pair(l.first + r.first, l.second + r.second); }
template<typename T1, typename T2> pair<T1, T2> operator-(const pair<T1, T2> &l, const pair<T1, T2> &r) { return make_pair(l.first - r.first, l.second - r.second); }
#define dbg(x) cerr << #x << " = " << (x) << " (L" << __LINE__ << ") " << __FILE__ << endl;
/*
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/tag_and_trait.hpp>
using namespace __gnu_pbds; // find_by_order(), order_of_key()
template<typename TK> using pbds_set = tree<TK, null_type, less<TK>, rb_tree_tag, tree_order_statistics_node_update>;
template<typename TK, typename TV> using pbds_map = tree<TK, TV, less<TK>, rb_tree_tag, tree_order_statistics_node_update>;
*/

vector<lint> v1, v2;

lint counter(vector<lint> &v, lint c) {
    // 積c未満を数える
    lint ret = 0;
    if (c <= 0) return 0;
    REP(i, v.size()) {
        if (v[i] == 0) {
            ret += v.size() - i - 1;
        }
        else {
            lint th = (c + v[i] - 1) / v[i];
            ret += lower_bound(v.begin() + i + 1, v.end(), th) - (v.begin() + i + 1);
        }
    }
    return ret;
}
lint cross_counter(lint c) {
    // 積がcより大きいものを数える
    lint ret = 0;
    for (auto x : v1) if (x) {
        lint tgt = c / x + 1;
        ret += v2.end() - lower_bound(v2.begin(), v2.end(), tgt);
    }
    return ret;
}
lint nb_zero;

lint solve(lint c) {
    lint cnt = 0;
    if (c > 0)
    {
        cnt += lint(v1.size()) * lint(v2.size());
        cnt += counter(v1, c) + counter(v2, c);
    }
    else if (c == 0)
    {
        cnt = lint(v1.size() - nb_zero) * v2.size();
    }
    else
    {
        cnt += cross_counter(abs(c));
    }
    return cnt;
}

int main()
{
    lint N, K;
    cin >> N >> K;
    vector<lint> A(N);
    cin >> A;
    for (auto x : A) {
        if (x < 0) v2.emplace_back(-x);
        else v1.emplace_back(x);
    }
    nb_zero = 0;
    for (auto x : A) nb_zero += (x == 0);

    sort(ALL(v2));
    sort(ALL(v1));

    lint lo = -1.1e18, hi = 1.1e18;
    while (hi - lo > 1) {
        lint c = lo + (hi - lo) / 2;
        lint cnt = solve(c);
        (cnt >= K ? hi : lo) = c;
    }
    // dbg(K);
    // dbg(solve(hi));
    // dbg(solve(lo));
    cout << lo << endl;
    // if (solve(hi) - solve(lo) == 1) cout << lo << endl;
    // else cout << hi << endl;
}


Measured memory_bytes: 4084