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

template<class T>
bool chmax(T& a, const T& b) {
    if (a < b) { a = b; return true; }
    return false;
}
template<class T>
bool chmin(T& a, const T& b) {
    if (b < a) { a = b; return true; }
    return false;
}

// std::vector Declaration
template<typename T>
vector<T> make_v(size_t a) { return vector<T>(a); }
template<typename T, typename... Ts>
auto make_v(size_t a, Ts... ts) {
    return vector<decltype(make_v<T>(ts...))>(a, make_v<T>(ts...));
}

// std::vector Declaration and Initialization
template<typename T>
vector<T> make_vector(size_t a, T x) { return vector<T>(a, x); }
template<typename T, typename U, typename... Ts>
auto make_vector(size_t a, U b, Ts... ts) {
    return vector<decltype(make_vector<T>(b,ts...))>(a, make_vector<T>(b, ts...));
}

// std::vector Input
template<typename T>
istream& operator>>(istream& is, vector<T>& v) {
    for (auto &e : v) is >> e;
    return is;
}

// std::vector Debug
template<typename T>
ostream& operator<<(ostream& os, const vector<T>& v) {
    os << "[";
    bool a = 1;
    for (auto e : v) {
        os << (a ? "" : " ");
        os << e;
        a = 0;
    }
    os << "]";
    return os;
}

// std::array Debug
template<typename T, size_t n>
ostream& operator<<(ostream& os, const array<T, n>& v) {
    os << "[";
    bool a = 1;
    for (auto e : v) {
        os << (a ? "" : " ");
        os << e;
        a = 0;
    }
    os << "]";
    return os;
}

// std::deque Debug
template<typename T>
ostream& operator<<(ostream& os, const deque<T>& d) {
    os << "[";
    bool a = 1;
    for (auto e : d) {
        os << (a ? "" : " ");
        os << e;
        a = 0;
    }
    os << "]";
    return os;
}

// std::pair Debug
template<typename T, typename U>
ostream& operator<<(ostream& os, const pair<T, U>& p) {
    os << "(" << p.first << " " << p.second << ")";
    return os;
}

// std::set Debug
template<typename T>
ostream& operator<<(ostream& os, const set<T>& st) {
    os << "{";
    bool a = 1;
    for (auto e : st) {
        os << (a ? "" : " ");
        os << e;
        a = 0;
    }
    os << "}";
    return os;
}

// std::multiset Debug
template<typename T>
ostream& operator<<(ostream& os, const multiset<T>& st) {
    os << "{";
    bool a = 1;
    for (auto e : st) {
        os << (a ? "" : " ");
        os << e;
        a = 0;
    }
    os << "}";
    return os;
}

// std::map Debug
template<typename T, typename U>
ostream& operator<<(ostream& os, const map<T, U>& mp) {
    os << "{";
    bool a = 1;
    for (auto e : mp) {
        os << (a ? "" : " ");
        os << e.first << ":" << e.second;
        a = 0;
    }
    os << "}";
    return os;
}

// std::tuple Debug
template<int N, class Tuple>
void out(ostream& os, const Tuple& t){}
template<int N, class Tuple, class H, class ...Ts>
void out(ostream& os, const Tuple& t) {
    if (N) os << " ";
    os << get<N>(t);
    out<N+1,Tuple,Ts...>(os, t);
}
template<class ...Ts>
ostream& operator<<(ostream& os, const tuple<Ts...>& t) {
    os << "(";
    out<0,tuple<Ts...>,Ts...>(os, t);
    os << ")";
    return os;
}

// Debug
#define DUMP(x) cerr<<#x<<" = "<<(x)<<endl

// Weighted edge
template<typename T>
struct edge {
    int src, to;
    T cost;

    edge(int to, T cost) : src(-1), to(to), cost(cost) {}
    edge(int src, int to, T cost) : src(src), to(to), cost(cost) {}

    friend ostream& operator<<(ostream& os, const edge& e) {
        return os << "(" << e.src << "->" << e.to << ":" << e.cost << ")";
    }
};

using LL = long long;

#define fs first
#define sc second

const LL MOD = 1e9+7;


int main()
{
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);

    LL N, K; cin >> N >> K;
    vector<LL> A(N); cin >> A;

    vector<LL> neg, zero, pos;
    for (LL a : A) {
        if (a < 0) neg.emplace_back(-a);
        if (a == 0) zero.emplace_back(0);
        if (a > 0) pos.emplace_back(a);
    }
    sort(neg.begin(), neg.end());
    sort(zero.begin(), zero.end());
    sort(pos.begin(), pos.end());

    LL ns = neg.size(),
       zs = zero.size(),
       ps = pos.size();

    LL nc = ns * ps,
       zc = zs * (ns + ps) + zs * (zs-1) / 2,
       pc = ns * (ns-1) / 2 + ps * (ps-1) / 2;


    const LL MAX = 1e18;

    if (K <= nc) {

        auto check = [&](LL v) {
            LL total = 0;
            // 絶対値v 以上の組合せの総数を求める
            for (LL n : neg) {
                auto lb = lower_bound(pos.begin(), pos.end(), (v-1)/n+1);
                total += distance(lb, pos.end());
            }
            return total <= K-1;
        };

        LL ng = 0, ok = MAX;
        while (abs(ng - ok) > 1) {
            LL mid = (ng + ok) / 2;
            (check(mid) ? ok : ng) = mid;
        }

        cout << -ng << endl;

    } else if (K <= nc + zc) {

        cout << 0 << endl;

    } else {

        K -= nc + zc;

        auto check = [&](LL v) {
            LL total = 0;
            // 絶対値v 以下の組合せの総数を求める
            for (LL n : neg) {
                auto ub = upper_bound(neg.begin(), neg.end(), v/n);
                total += distance(neg.begin(), ub);
            }
            for (LL n : neg) {
                if (n*n <= v) --total;
            }

            for (LL p : pos) {
                auto ub = upper_bound(pos.begin(), pos.end(), v/p);
                total += distance(pos.begin(), ub);
            }
            for (LL p : pos) {
                if (p*p <= v) --total;
            }

            return total / 2 >= K;
        };

        LL ng = 0, ok = MAX;
        while (abs(ng - ok) > 1) {
            LL mid = (ng + ok) / 2;
            (check(mid) ? ok : ng) = mid;
        }

        cout << ok << endl;
    }

    return 0;
}


Measured memory_bytes: 4084