#include <bits/stdc++.h>

using namespace std;


using int64 = long long;
const int mod = 1e9 + 7;

const int64 infll = (1LL << 62) - 1;
const int inf = (1 << 30) - 1;

struct IoSetup {
  IoSetup() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(10);
    cerr << fixed << setprecision(10);
  }
} iosetup;


template< typename T1, typename T2 >
ostream &operator<<(ostream &os, const pair< T1, T2 > &p) {
  os << p.first << " " << p.second;
  return os;
}

template< typename T1, typename T2 >
istream &operator>>(istream &is, pair< T1, T2 > &p) {
  is >> p.first >> p.second;
  return is;
}

template< typename T >
ostream &operator<<(ostream &os, const vector< T > &v) {
  for(int i = 0; i < (int) v.size(); i++) {
    os << v[i] << (i + 1 != v.size() ? " " : "");
  }
  return os;
}

template< typename T >
istream &operator>>(istream &is, vector< T > &v) {
  for(T &in : v) is >> in;
  return is;
}

template< typename T1, typename T2 >
inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }

template< typename T1, typename T2 >
inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }

template< typename T = int64 >
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...));
}

template< typename T, typename V >
typename enable_if< is_class< T >::value == 0 >::type fill_v(T &t, const V &v) {
  t = v;
}

template< typename T, typename V >
typename enable_if< is_class< T >::value != 0 >::type fill_v(T &t, const V &v) {
  for(auto &e : t) fill_v(e, v);
}

template< typename F >
struct FixPoint : F {
  FixPoint(F &&f) : F(forward< F >(f)) {}

  template< typename... Args >
  decltype(auto) operator()(Args &&... args) const {
    return F::operator()(*this, forward< Args >(args)...);
  }
};

template< typename F >
inline decltype(auto) MFP(F &&f) {
  return FixPoint< F >{forward< F >(f)};
}


int main() {
  int64 N, K;
  cin >> N >> K;
  vector< int64 > A(N);
  cin >> A;
  sort(begin(A), end(A));

  int64 zero = 0;
  vector< int64 > neg, pos, negrev;
  for(int i = 0; i < N; i++) {
    if(A[i] == 0) ++zero;
    else if(A[i] < 0) neg.emplace_back(A[i]), negrev.emplace_back(-A[i]);
    else pos.emplace_back(A[i]);
  }

  sort(begin(negrev), end(negrev));

  // lim以下の要素の個数
  auto check = [&](int64 lim) {
    int64 ret = 0;
    if(lim >= 0) {
      ret += zero * (zero - 1) / 2;
      ret += zero * (int64) neg.size();
      ret += zero * (int64) pos.size();
    }
    if(lim > 0) {
      int64 add = 0;
      for(int i = 0; i < negrev.size(); i++) {
        // neg*neg
        int64 uku = lim / negrev[i] + 1;
        add += lower_bound(begin(negrev), end(negrev), uku) - begin(negrev);
        add -= negrev[i] < uku;
      }
      for(int i = 0; i < pos.size(); i++) {
        // pos*pos
        int64 uku = lim / pos[i] + 1;
        add += lower_bound(begin(pos), end(pos), uku) - begin(pos);
        add -= pos[i] < uku;
      }
      add /= 2;


      ret += add;
    }

    {
      // neg*pos
      int64 add = 0;
      for(int i = 0; i < negrev.size(); i++) {
        if(lim >= 0) {
          add += pos.size();
        } else {
          // -lim以上ならばよいので
          int64 need = (-lim + negrev[i] - 1) / negrev[i];
          int uku = lower_bound(begin(pos), end(pos), need) - begin(pos);
          add += pos.size() - uku;
        }
      }
      ret += add;
    }
    return ret;
  };

  int64 low = -infll, high = infll;
  while(high - low > 1) {
    int64 mid = (low + high) / 2;
    if(check(mid) >= K) high = mid;
    else low = mid;
  }
  cout << high << endl;
}


Measured memory_bytes: 5100