#include <bits/stdc++.h>
#include <cassert>
typedef long long int ll;
using namespace std;

// @@ !! LIM(debug binsearch)
// --> f:<< debug binsearch
// ---- inserted function << from util.cc
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, typename T3>
ostream& operator<< (ostream& os, const tuple<T1,T2,T3>& t) {
  os << "(" << get<0>(t) << ", " << get<1>(t)
     << ", " << get<2>(t) << ")";
  return os;
}

template <typename T1, typename T2, typename T3, typename T4>
ostream& operator<< (ostream& os, const tuple<T1,T2,T3,T4>& t) {
  os << "(" << get<0>(t) << ", " << get<1>(t)
     << ", " << get<2>(t) << ", " << get<3>(t) << ")";
  return os;
}

template <typename T>
ostream& operator<< (ostream& os, const vector<T>& v) {
  os << '[';
  for (auto it = v.begin(); it != v.end(); it++) {
    if (it != v.begin()) os << ", ";
    os << *it;
  }
  os << ']';

  return os;
}

template <typename T>
ostream& operator<< (ostream& os, const set<T>& v) {
  os << '{';
  for (auto it = v.begin(); it != v.end(); it++) {
    if (it != v.begin()) os << ", ";
    os << *it;
  }
  os << '}';

  return os;
}

template <typename T>
ostream& operator<< (ostream& os, const multiset<T>& v) {
  os << '{';
  for (auto it = v.begin(); it != v.end(); it++) {
    if (it != v.begin()) os << ", ";
    os << *it;
  }
  os << '}';

  return os;
}

template <typename T1, typename T2>
ostream& operator<< (ostream& os, const map<T1, T2>& mp) {
  os << '[';
  for (auto it = mp.begin(); it != mp.end(); it++) {
    if (it != mp.begin()) os << ", ";
    os << it->first << ": " << it->second;
  }
  os << ']';

  return os;
}

template <typename T, typename T2, typename T3>
ostream& operator<< (ostream& os, const priority_queue<T, T2, T3>& orig) {
  priority_queue<T, T2, T3> pq(orig);
  bool first = true;
  os << '[';
  while (!pq.empty()) {
    T x = pq.top(); pq.pop();
    if (!first) os << ", ";
    os << x;
    first = false;
  }
  return os << ']';
}
// ---- end <<
// ---- inserted library file debug.cc
template <class... Args>
string dbgFormat(const char* fmt, Args... args) {
  size_t len = snprintf(nullptr, 0, fmt, args...);
  char buf[len + 1];
  snprintf(buf, len + 1, fmt, args...);
  return string(buf);
}

template <class Head>
void dbgLog(Head&& head) {
  cerr << head << endl;
}

template <class Head, class... Tail>
void dbgLog(Head&& head, Tail&&... tail)
{
  cerr << head << " ";
  dbgLog(forward<Tail>(tail)...);
}

#if DEBUG
  #define DLOG(...)        dbgLog(__VA_ARGS__)
  #define DFMT(...)        cerr << dbgFormat(__VA_ARGS__) << endl
  #define DCALL(func, ...) func(__VA_ARGS__)
#else
  #define DLOG(...)
  #define DFMT(...)
  #define DCALL(func, ...)
#endif

// ---- end debug.cc
// ---- inserted library file binsearch.cc

template<typename T>
T binsearch(auto check, T yes, T no, T err = (T)1) {
  while (abs(yes - no) > err) {
    T mid = (yes + no) / (T)2;
    if (check(mid)) yes = mid;
    else            no  = mid;
  }
  return yes;
}

// ---- end binsearch.cc
// @@ !! LIM  -- end mark --

int main(int argc, char *argv[]) {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout << setprecision(20);

  ll N, K; cin >> N >> K;
  vector<ll> A(N);
  for (ll i = 0; i < N; i++) cin >> A.at(i);
  sort(A.begin(), A.end());
  vector<ll> B(A);
  for (ll i = 0; i < N; i++) B.at(i) = B.at(i) * B.at(i);
  sort(B.begin(), B.end());

  // func1(t) == true if |{(x,y) : x*y <= t}| >= K
  auto func1 = [&](ll t) {
    ll cnt = 0;
    for (ll i = 0; i < N; i++) {
      if (A.at(i) == 0) {
	if (t >= 0) cnt += N;
	else        cnt += 0;
      }else if (A.at(i) > 0) {
	ll j = binsearch<ll>([&](ll k){ return A.at(i) * A.at(k) <= t; },
			     -1, N);
	cnt += j + 1;
      }else if (A.at(i) < 0) {
	ll j = binsearch<ll>([&](ll k){ return A.at(i) * A.at(k) <= t; },
			     N, -1);
	cnt += N - j;
      }else assert(0);
    }
    ll cnt2 = 1 + binsearch<ll>([&](ll k) { return B.at(k) <= t; }, -1, N);
    ll cntPair = (cnt - cnt2) / 2;
    return cntPair >= K;
  };

  ll big = 1e18;
  ll small = -1e18;
  ll ans = binsearch(func1, big, small);
  cout << ans << endl;
  return 0;
}



Measured memory_bytes: 3456