/*** Template Begin ***/

#pragma region template

#define USING_NAMESPACE

#include <algorithm>
#include <array>
#include <bitset>
#include <cassert>
#include <cmath>
#include <complex>
#include <cstdio>
#include <cstdlib>
#include <deque>
#include <functional>
#include <iomanip>
#include <iostream>
#include <list>
#include <map>
#include <numeric>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <string>
#include <tuple>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

typedef int64_t i64;
typedef uint64_t u64;

auto init_ = [] {
    std::ios_base::sync_with_stdio(false);
    std::cout << std::fixed;
    return 0;
}();

template <typename T>
inline void in(T &x) {
    std::cin >> x;
}

template <typename T, typename... Ts>
inline void in(T &t, Ts &... ts) {
    std::cin >> t;
    in(ts...);
}

template <typename T, typename U = std::vector<T>>
inline U vin(int n) {
    U v(n);
    for (int i = 0; i < n; ++i) {
        std::cin >> v[i];
    }
    return v;
}

template <typename T, typename U = std::vector<T>, typename V = std::vector<U>>
inline V vin(int h, int w) {
    V vv(h, U(w));
    for (int i = 0; i < h; ++i) {
        for (int j = 0; j < w; ++j) {
            std::cin >> vv[i][j];
        }
    }
    return vv;
}

template <typename T>
inline void out(const T &x) {
    std::cout << x << std::endl;
}

template <char delimiter = ' ', typename T, typename... Ts>
inline void out(const T &t, const Ts &... ts) {
    std::cout << t << delimiter;
    out(ts...);
}

template <char delimiter = ' ', typename T>
inline void vout(const T &v, int n) {
    for (int i = 0; i < n; ++i) {
        if (i) std::cout << delimiter;
        std::cout << v[i];
    }
    std::cout << std::endl;
}

template <char delimiter = ' ', typename T>
inline void vout(const T &v, int h, int w) {
    for (int i = 0; i < h; ++i) {
        for (int j = 0; j < w; ++j) {
            if (j) std::cout << delimiter;
            std::cout << v[i][j];
        }
        std::cout << std::endl;
    }
}

template <typename T, size_t D>
struct multi_vector_type {
    using type = std::vector<typename multi_vector_type<T, D - 1>::type>;
};

template <typename T>
struct multi_vector_type<T, 1> {
    using type = std::vector<T>;
};

template <typename T>
struct multi_vector_type<T, 0> {
    using type = T;
};

template <typename T, size_t D>
using multi_vector = typename multi_vector_type<T, D>::type;

template <typename T, size_t D, class = typename std::enable_if<D == 0>::type>
T make_vector(const T &val = T()) {
    return val;
}

template <typename T, size_t D = 1, typename... Ts,
          class = typename std::enable_if<D != 0>::type>
multi_vector<T, D> make_vector(size_t n, Ts &&... args) {
    return multi_vector<T, D>(n, make_vector<T, D - 1>(args...));
}

namespace detail {

template <typename F>
struct Debug {
    const char *delim_ = "\n";
    F fun;

    Debug(F f) : fun(f) {}

    ~Debug() { fun(delim_); }

    Debug &delim(const char *d) {
        delim_ = d;
        return *this;
    }
};

std::deque<std::string> split(const std::string &s, char c) {
    std::deque<std::string> v;
    std::stringstream ss(s);
    std::string x;
    while (std::getline(ss, x, c)) v.emplace_back(x);
    return v;
}

template <typename T>
void deb(const char *delim, std::deque<std::string> v, T a) {
    std::cerr << v[0].substr(v[0][0] == ' ', v[0].length()) << " = " << a
              << '\n';
    std::cerr << std::flush;
}

template <typename T, typename... Args>
void deb(const char *delim, std::deque<std::string> v, T a, Args... args) {
    std::cerr << v[0].substr(v[0][0] == ' ', v[0].length()) << " = " << a
              << delim;
    v.pop_front();
    deb(delim, std::move(v), args...);
}

template <typename... Args>
auto wrap(std::deque<std::string> v, Args... args) {
    auto f = [=](const char *delim = "\n") { deb(delim, v, args...); };

    return Debug<decltype(f)>(f);
}
}

#define debug(args...) ::detail::wrap(::detail::split(#args, ','), args)

#ifdef USING_BOOST

#include <boost/math/common_factor.hpp>
#include <boost/range.hpp>
#include <boost/range/adaptors.hpp>
#include <boost/range/algorithm.hpp>
#include <boost/range/algorithm_ext.hpp>
#include <boost/range/irange.hpp>
#include <boost/range/numeric.hpp>

inline auto rep(int begin, int end) {
    if (begin > end) {
        return boost::irange(0, 0);
    } else {
        return boost::irange(begin, end);
    }
}

inline auto rep(int begin, int end, int step) {
    if ((step > 0 && begin > end) || (step < 0 && begin < end)) {
        return boost::irange(0, 0, step);
    } else {
        return boost::irange(begin, end, step);
    }
}

#endif

#ifdef USING_NAMESPACE
using namespace std;

#ifdef USING_BOOST
using namespace boost;
using namespace boost::adaptors;
#endif
#endif

#pragma endregion

/*** Template End ***/

int main() {
    i64 n, k;
    in(n, k);

    auto a = vin<i64>(n);

    vector<i64> p, m;

    for (i64 x : a) {
        if (x < 0) {
            m.push_back(-x);
        } else {
            p.push_back(x);
        }
    }

    sort(p.begin(), p.end());
    sort(m.begin(), m.end());

    i64 ng = -2e18;
    i64 ok = 2e18;

    // i64 ng = -20;
    // i64 ok = 20;

    while(ok - ng > 1) {
        i64 mid = (ng + ok) / 2;
    
        // mid >= Ai * Aj (i, j) 
        i64 cnt = 0;

        if (mid < 0) {
            // m * p

            i64 abs_mid = -mid;

            // pi * mj >= abs_mid

            int r = (int)m.size() - 1;

            if (m.size() > 0) {
                for (int i = 0; i < p.size(); i++) {
                    if (p[i] * m.back() < abs_mid) {
                        continue;
                    }

                    while(r >= 0 && m[r] * p[i] >= abs_mid) {
                        r--;
                    }

                    cnt += m.size() - r - 1;
                }
            }
        } else {
            // m * m or p * p

            cnt += p.size() * m.size();
            //out(cnt);
            // count mj <= mid / mi
            {
                int l = 0;
                for (int i = (int)m.size() - 1; i >= 1; i--) {
                    while (l <= i && m[i] * m[l] <= mid) {
                        l++;
                    }

                    if (l >= i) {
                        cnt += i;
                    } else {
                        cnt += l;
                    }
                }
            }
            //out(cnt);

            // count pj <= mid / pi
            {
                int l = 0;
                for (int i = (int)p.size() - 1; i >= 1; i--) {
                    while (l <= i && p[i] * p[l] <= mid) {
                        l++;
                    }

                    if (l >= i) {
                        cnt += i;
                    } else {
                        cnt += l;
                    }
                }
            }

            //out(cnt);
        }

        //out(mid, cnt);

        if (cnt >= k) {
            ok = mid;
        } else {
            ng = mid;
        }
    }

    out(ok);
}

Measured memory_bytes: 4084