/* #region Head */

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

using ll = long long;
using ull = unsigned long long;
using ld = long double;
using pll = pair<ll, ll>;
template <class T>
using vc = vector<T>;
template <class T>
using vvc = vc<vc<T>>;
using vll = vc<ll>;
using vvll = vvc<ll>;
using vld = vc<ld>;
using vvld = vvc<ld>;
using vs = vc<string>;
using vvs = vvc<string>;
template <class T, class U>
using um = unordered_map<T, U>;

#define REP(i, m, n) for (ll i = (m), i##_len = (ll)(n); i < i##_len; ++(i))
#define REPM(i, m, n) for (ll i = (m), i##_max = (ll)(n); i <= i##_max; ++(i))
#define REPR(i, m, n) for (ll i = (m), i##_min = (ll)(n); i >= i##_min; --(i))
#define REPD(i, m, n, d) for (ll i = (m), i##_len = (ll)(n); i < i##_len; i += (d))
#define REPMD(i, m, n, d) for (ll i = (m), i##_max = (ll)(n); i <= i##_max; i += (d))
#define REPI(itr, ds) for (auto itr = ds.begin(); itr != ds.end(); itr++)
#define ALL(x) begin(x), end(x)
#define SIZE(x) ((ll)(x).size())
#define PREM(c)   \
    sort(all(c)); \
    for (bool c##p = 1; c##p; c##p = next_permutation(all(c)))
#define UNIQ(v) v.erase(unique(ALL(v)), v.end());
#define fs first
#define sc second
#define pb push_back

constexpr ll INF = 1'010'000'000'000'000'017LL;
constexpr ll MOD = 1'000'000'007LL; // 1e9 + 7
constexpr ld EPS = 1e-12;
constexpr ld PI = 3.14159265358979323846;

// vector 入力
template <typename T>
istream &operator>>(istream &is, vc<T> &vec)
{
    for (T &x : vec)
        is >> x;
    return is;
}

// vector 出力 (for dump)
template <typename T>
ostream &operator<<(ostream &os, vc<T> &vec)
{
    ll len = SIZE(vec);
    os << "{";
    for (int i = 0; i < len; i++)
        os << vec[i] << (i == len - 1 ? "" : ", ");
    os << "}";
    return os;
}

// vector 出力 (inline)
template <typename T>
ostream &operator>>(ostream &os, vc<T> &vec)
{
    ll len = SIZE(vec);
    for (int i = 0; i < len; i++)
        os << vec[i] << (i == len - 1 ? "\n" : " ");
    return os;
}

// pair 入力
template <typename T, typename U>
istream &operator>>(istream &is, pair<T, U> &pair_var)
{
    is >> pair_var.first >> pair_var.second;
    return is;
}

// pair 出力
template <typename T, typename U>
ostream &operator<<(ostream &os, pair<T, U> &pair_var)
{
    os << "(" << pair_var.first << ", " << pair_var.second << ")";
    return os;
}

// map 出力
template <typename T, typename U>
ostream &operator<<(ostream &os, map<T, U> &map_var)
{
    os << "{";
    REPI(itr, map_var)
    {
        os << *itr;
        itr++;
        if (itr != map_var.end())
            os << ", ";
        itr--;
    }
    os << "}";
    return os;
}

// um 出力
template <typename T, typename U>
ostream &operator<<(ostream &os, um<T, U> &map_var)
{
    os << "{";
    REPI(itr, map_var)
    {
        os << *itr;
        auto itrcp = itr;
        itrcp++;
        if (itrcp != map_var.end())
            os << ", ";
    }
    os << "}";
    return os;
}

// set 出力
template <typename T>
ostream &operator<<(ostream &os, set<T> &set_var)
{
    os << "{";
    REPI(itr, set_var)
    {
        os << *itr;
        itr++;
        if (itr != set_var.end())
            os << ", ";
        itr--;
    }
    os << "}";
    return os;
}

// dump
#define DUMPOUT cerr
void dump_func()
{
    DUMPOUT << endl;
}
template <class Head, class... Tail>
void dump_func(Head &&head, Tail &&... tail)
{
    DUMPOUT << head;
    if (sizeof...(Tail) > 0)
    {
        DUMPOUT << ", ";
    }
    dump_func(move(tail)...);
}

// chmax (更新「される」かもしれない値が前)
template <typename T, typename U, typename Comp = less<>>
bool chmax(T &xmax, const U &x, Comp comp = {})
{
    if (comp(xmax, x))
    {
        xmax = x;
        return true;
    }
    return false;
}

// chmin (更新「される」かもしれない値が前)
template <typename T, typename U, typename Comp = less<>>
bool chmin(T &xmin, const U &x, Comp comp = {})
{
    if (comp(x, xmin))
    {
        xmin = x;
        return true;
    }
    return false;
}

// ローカル用
#define DEBUG_

#ifdef DEBUG_
#define DEB
#define dump(...)                                                       \
    DUMPOUT << "  " << string(#__VA_ARGS__) << ": "                     \
            << "[" << to_string(__LINE__) << ":" << __FUNCTION__ << "]" \
            << endl                                                     \
            << "    ",                                                  \
        dump_func(__VA_ARGS__)
#else
#define DEB if (false)
#define dump(...)
#endif

struct AtCoderInitialize
{
    static constexpr int IOS_PREC = 15;
    static constexpr bool AUTOFLUSH = false;

    AtCoderInitialize()
    {
        ios_base::sync_with_stdio(false);
        cin.tie(nullptr);
        cout.tie(nullptr);
        cout << fixed << setprecision(IOS_PREC);
        if (AUTOFLUSH)
            cout << unitbuf;
    }
} ATCODER_INITIALIZE;

/* #endregion */

template <class tProposition>
ll binarySearchIntMin(ll left, ll right, tProposition p)
{
    if (right < left)
        return -1;
    ll mid, fn;
    while (left + 1 < right)
    {
        mid = (left + right) / 2;
        if (p(mid))
            right = mid;
        else // fn > 0
            left = mid + 1;
    }

    if (p(left))
        return left;
    else if (p(right))
        return right;
    else
        return -1;
}

/**
Problem
 */
void solve()
{
    ll n, k;
    cin >> n >> k;
    vll a(n);
    cin >> a;

    sort(ALL(a));
    ll cnt_negative = 0, cnt_zero = 0, cnt_positive = 0;
    vll positives, negatives;
    REP(i, 0, n)
    {
        if (a[i] < 0)
            cnt_negative++, negatives.push_back(a[i]);
        else if (a[i] == 0)
            cnt_zero++;
        else
            cnt_positive++, positives.push_back(a[i]);
    }
    // dump(cnt_negative, cnt_positive);
    ll cnt_pair_negative = cnt_negative * cnt_positive;                                                   // 負×正
    ll cnt_pair_positive = cnt_negative * (cnt_negative - 1) / 2 + cnt_positive * (cnt_positive - 1) / 2; // 負×負，正×正
    ll cnt_pair_zero = n * (n - 1) / 2 - cnt_pair_negative - cnt_pair_positive;                           // その他
    // dump(cnt_pair_negative, cnt_pair_positive);

    // 0
    if (cnt_pair_negative < k && k <= cnt_pair_negative + cnt_pair_zero)
    {
        cout << 0 << endl;
        return;
    }

    // 正
    if (cnt_pair_negative + cnt_pair_zero < k)
    {
        ll num_in_positive = k - (cnt_pair_negative + cnt_pair_zero); // 正の数のうちで num_in_positive 番目を探す

        // dump(num_in_positive);
        // num_in_positive 番目の値を求める
        // → 値を決め打ちして，その値以下が何個あるか数える
        // → 個数が num_in_positive 以上になるような最小の値が答え
        ll val = binarySearchIntMin(1, std::max(a[0] * a[0], a[n - 1] * a[n - 1]), [&](ll th) {
            ll cnt1 = 0;
            vll::iterator it;

            // 正×正
            REP(i, 0, cnt_positive)
            {
                // positives[i] * positives[j] <=  th なる個数
                // = n - (positives[i] * positives[j] > th なる個数)
                // = n - (positives[j] > th / positives[i] なる個数)
                it = upper_bound(ALL(positives), th / positives[i]);
                cnt1 += cnt_positive - (positives.end() - it);
                if (positives[i] * positives[i] <= th)
                    --cnt1;
            }
            cnt1 /= 2;

            ll cnt2 = 0;
            // 負×負
            REP(i, 0, cnt_negative)
            {
                // negatives[i] * negatives[j] <=  th なる個数
                // = negatives[j] >=  th / negatives[i] なる個数
                it = lower_bound(ALL(negatives), -(th / -negatives[i]));
                cnt2 += negatives.end() - it;
                if (negatives[i] * negatives[i] <= th)
                    --cnt2;
            }
            cnt2 /= 2;

            // dump(th, cnt);
            return cnt1 + cnt2 >= num_in_positive;
        });
        std::cout << val << endl;
        return;
    }

    // dump(positives, negatives);
    // 負
    // k 番目の値を求める
    // → 値を決め打ちして，その値以下が何個あるか数える
    // → 個数が k 以上になるような最小の値が答え
    ll val = binarySearchIntMin(a[0] * a[n - 1], -1, [&](ll th) {
        ll cnt = 0;
        vll::iterator it;

        // 負×正
        REP(i, 0, cnt_negative)
        {
            // negatives[i] * positives[j] <=  th なる個数
            // = positives[j] >=  ceil(-th / -negatives[i]) なる個数
            // dump(negatives[i], th, (-th - negatives[i] - 1) / -negatives[i]);
            it = lower_bound(ALL(positives), (-th - negatives[i] - 1) / -negatives[i]);
            // ll c = positives.end() - it;
            // dump(c);
            cnt += positives.end() - it;
        }
        // dump(th, cnt);
        return cnt >= k;
    });
    cout << val << endl;
    return;
}

/**
 * エントリポイント．
 * @return 0.
 */
int main()
{
    solve();
    return 0;
}


Measured memory_bytes: 4084