#include <bits/stdc++.h>

using namespace std;

#define REP(i, N) for (int i = 0; i < (int)N; i++)
#define FOR(i, a, b) for (int i = a; i < (int)b; i++)
#define ALL(x) (x).begin(), (x).end()
#define INF (1 << 30)
#define LLINF (1LL << 62)
#define DEBUG(...) debug(__LINE__, ":" __VA_ARGS__)

constexpr int MOD = 1000000007;
using ll = long long;
using Pii = pair<int, int>;
using Pll = pair<ll, ll>;

template <class T>
string to_string(T s);
template <class S, class T>
string to_string(pair<S, T> p);
string to_string(string s);
string to_string(const char s[]) { return string(s); }

template <class T>
string to_string(T v) {
  if (v.empty()) return "{}";
  string ret = "{";
  auto itr = v.begin(), next = ++v.begin();
  for (; next != v.end(); ++itr, ++next) ret += to_string(*itr) + ",";
  ret += to_string(*itr) + "}";
  return ret;
}
template <class S, class T>
string to_string(pair<S, T> p) {
  return "{" + to_string(p.first) + "," + to_string(p.second) + "}";
}
string to_string(string s) { return s; }

void debug() { cerr << endl; }
template <class Head, class... Tail>
void debug(Head head, Tail... tail) {
  cerr << to_string(head) << " ";
  debug(tail...);
}
void print() { cout << endl; }
template <class Head, class... Tail>
void print(Head head, Tail... tail) {
  cout << to_string(head) << " ";
  print(tail...);
}

struct IO {
#ifdef _WIN32
  inline char getchar_unlocked() { return getchar(); }
  inline void putchar_unlocked(char c) { putchar(c); }
#endif
  string separator = " ";
  template <class T>
  inline void read(T &x) {
    char c;
    do {
      c = getchar_unlocked();
    } while (c != '-' && (c < '0' || '9' < c));
    bool minus = 0;
    if (c == '-') {
      minus = 1;
      c = getchar_unlocked();
    }
    x = 0;
    while ('0' <= c && c <= '9') {
      x *= 10;
      x += c - '0';
      c = getchar_unlocked();
    }
    if (minus) x = -x;
  }
  inline void read(string &x) {
    char c;
    do {
      c = getchar_unlocked();
    } while (c == ' ' || c == '\n');
    x.clear();
    do {
      x += c;
      c = getchar_unlocked();
    } while (c != ' ' && c != '\n' && c != EOF);
  }
  template <class T>
  inline void read(vector<T> &v) {
    for (auto &x : v) read(x);
  }
  template <class Head, class... Tail>
  inline void read(Head &head, Tail &... tail) {
    read(head);
    read(tail...);
  }
  template <class T>
  inline void write(T x) {
    char buf[32];
    int p = 0;
    if (x < 0) {
      x = -x;
      putchar_unlocked('-');
    }
    if (x == 0) putchar_unlocked('0');
    while (x > 0) {
      buf[p++] = (x % 10) + '0';
      x /= 10;
    }
    while (p) {
      putchar_unlocked(buf[--p]);
    }
  }
  inline void write(string x) {
    for (char c : x) putchar_unlocked(c);
  }
  inline void write(const char s[]) {
    for (int i = 0; s[i] != 0; ++i) putchar_unlocked(s[i]);
  }
  template <class T>
  inline void write(vector<T> v) {
    for (auto itr = v.begin(); itr + 1 != v.end(); ++itr) {
      write(*itr);
      write(separator);
    }
    write(v.back());
  }
  template <class Head, class... Tail>
  inline void write(Head head, Tail... tail) {
    write(head);
    write(separator);
    write(tail...);
  }
  void set_separator(string s) { separator = s; }
} io;

int main() {
  ll N, K;
  io.read(N, K);
  vector<ll> A(N);
  io.read(A);
  sort(ALL(A));
  int neg_num = lower_bound(ALL(A), 0LL) - A.begin();
  ll l = -1e18 - 1, r = 1e18 + 1;
  while (l + 1 != r) {
    ll m = l + (r - l) / 2, t = 0;
    REP(i, N - 1) {
      ll rate = A[i] != 0 ? abs(m) / abs(A[i]) : 1e18;
      if (A[i] >= 0 && m >= 0) {
        t +=
            upper_bound(A.begin() + i + 1, A.end(), rate) - (A.begin() + i + 1);
      } else if (A[i] < 0 && m >= 0) {
        t += A.end() - lower_bound(A.begin() + i + 1, A.end(), -rate);
      } else if (A[i] >= 0 && m < 0) {
        t += upper_bound(A.begin() + i + 1, A.end(), -rate) -
             (A.begin() + i + 1);
      } else {
        t += A.end() -
             lower_bound(
                 A.begin() + i + 1, A.end(),
                 rate + ((A[i] == 0 || abs(m) % abs(A[i])) == 0 ? 0 : 1));
      }
    }
    // debug(l, r, m, t);
    if (t < K) {
      l = m;
    } else {
      r = m;
    }
  }
  cout << l + 1 << endl;
  return 0;
}

Measured memory_bytes: 1792