#include <iostream>
#include <iomanip>
#include <string>
#include <stack>
#include <vector>
#include <complex>
#include <math.h>
#include <stdio.h>
#include <algorithm>
#include <utility>
#include <functional>
#include <iterator>
#include <map>
#include <set>
#include <queue>
#include <list>
#include <regex>
#include <limits>
#include <time.h>
#include <cstdint>
using namespace std;
using pii  = pair<int,int>;
using ll=long long;
using ld=long double;
#define pb push_back
#define mp make_pair
#define sc second
#define fr first
#define stpr setprecision
#define cYES cout<<"YES"<<endl
#define cNO cout<<"NO"<<endl
#define cYes cout<<"Yes"<<endl
#define cNo cout<<"No"<<endl
#define rep(i,n) for(ll i=0;i<(n);++i)
#define Rep(i,a,b) for(ll i=(a);i<(b);++i)
#define rrep(i,n) for(ll i=n-1;i>=0;i--)
#define rRep(i,a,b) for(ll i=a;i>=b;i--)
#define crep(i) for(char i='a';i<='z';++i)
#define psortsecond(A,N) sort(A,A+N,[](const pii &a, const pii &b){return a.second<b.second;});
#define ALL(x) (x).begin(),(x).end()
#define debug(v) cout<<#v<<":";for(auto x:v){cout<<x<<' ';}cout<<endl;
#define endl '\n'
int ctoi(const char c){
  if('0' <= c && c <= '9') return (c-'0');
  return -1;
}
ll gcd(ll a,ll b){return (b == 0 ? a : gcd(b, a%b));}
ll lcm(ll a,ll b){return a*b/gcd(a,b);}
constexpr ll MOD=1000000007;
constexpr ll INF=1000000011;
constexpr ll MOD2=998244353;
constexpr ll LINF = 1001002003004005006ll;
constexpr ld EPS=10e-8;
template <class T, class U> inline bool chmax(T& lhs, const U& rhs) { if (lhs < rhs) { lhs = rhs; return 1; } return 0; }
template <class T, class U> inline bool chmin(T& lhs, const U& rhs) { if (lhs > rhs) { lhs = rhs; return 1; } return 0; }
template<typename T> istream& operator>>(istream& is,vector<T>& v){for(auto&& x:v)is >> x;return is;}
template<typename T,typename U> istream& operator>>(istream& is, pair<T,U>& p){ is >> p.first; is >> p.second; return is;}
template<typename T,typename U> ostream& operator>>(ostream& os, const pair<T,U>& p){ os << p.first << ' ' << p.second; return os;}
template<class T> ostream& operator<<(ostream& os, vector<T>& v){
  for(auto i=begin(v); i != end(v); ++i){
    if(i !=begin(v)) os << ' ';
    os << *i;
  }
  return os;
}

template <std::uint_fast64_t Modulus> class modint {
  using u64 = std::uint_fast64_t;

public:
  u64 a;

  constexpr modint(const u64 x = 0) noexcept : a(x % Modulus) {}
  constexpr u64 &value() noexcept { return a; }
  constexpr const u64 &value() const noexcept { return a; }
  constexpr modint operator+(const modint rhs) const noexcept {
    return modint(*this) += rhs;
  }
  constexpr modint operator-(const modint rhs) const noexcept {
    return modint(*this) -= rhs;
  }
  constexpr modint operator*(const modint rhs) const noexcept {
    return modint(*this) *= rhs;
  }
  constexpr modint operator/(const modint rhs) const noexcept {
    return modint(*this) /= rhs;
  }
  constexpr modint &operator+=(const modint rhs) noexcept {
    a += rhs.a;
    if (a >= Modulus) {
      a -= Modulus;
    }
    return *this;
  }
  constexpr modint &operator-=(const modint rhs) noexcept {
    if (a < rhs.a) {
      a += Modulus;
    }
    a -= rhs.a;
    return *this;
  }
  constexpr modint &operator*=(const modint rhs) noexcept {
    a = a * rhs.a % Modulus;
    return *this;
  }
  constexpr modint &operator/=(modint rhs) noexcept {
    u64 exp = Modulus - 2;
    while (exp) {
      if (exp % 2) {
        *this *= rhs;
      }
      rhs *= rhs;
      exp /= 2;
    }
    return *this;
  }
};

ll B,C,D,E,F,G,H,K,L,N,Q,R,U,W,X,Y,Z;
string S,T;
vector<ll> A,V;
map<string,ll> M;

bool check(ll key){
  Y=0;
  rep(i,A.size()){
    ll P=upper_bound(ALL(A),(ld)key/(ld)A[i])-A.begin();
    if(P>i){
      P--;
    }
    Y+=P;
  }
  rep(i,V.size()){
    ll P=V.end()-lower_bound(ALL(V),(ld)key/(ld)V[i]);
    if(P>V.size()-i){
      P--;
    }
    Y+=P;
  }
  Y/=2;
  if(Y<K){
    return 1;
  }
  else{
    return 0;
  }
}

bool check1(ll key){
  Y=0;
  rep(i,V.size()){
    ll P=upper_bound(ALL(A),(ld)key/(ld)V[i])-A.begin();
    Y+=A.size()-P;
  }
  if(Y<K){
    return 0;
  }
  else{
    return 1;
  }
}

int main(){
  cin >> N >> K;
  ll z=0;
  rep(i,N){
    cin >> X;
    if(X>0){
      A.pb(X);
    }
    else if(X==0){
      z++;
    }
    else{
      V.pb(X);
    }
  }
  sort(ALL(A));
  sort(ALL(V));
  ll X=A.size()*V.size();
  z=z*(A.size()+V.size())+(z*(z-1))/2;
  ll mid;
  if(X+z<K){
    K-=(X+z);
    ll ok=0,ng=LINF;
    while(ng-ok>1){
      mid = (ok+ng)/2;
      if(check(mid)){
        ok = mid;
      }
      else{
        ng = mid;
      }
    }
    cout << ok+1 << endl;
  }
  else if(X<K){
    cout << 0 << endl;
    return 0;
  }
  else{
    ll ok=0,ng=LINF;
    while(ng-ok>1){
      mid = (ok+ng)/2;
      if(check1(-mid)){
        ok = mid;
      }
      else{
        ng = mid;
      }
    }
    cout << -ok-1 << endl;
  }
} 

Measured memory_bytes: 2420