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



typedef unsigned long ul;
typedef unsigned long long ull;
typedef long long ll;
typedef vector<ll> vint;
typedef vector< vector<ll> > vvint;
typedef vector< vector< vector<ll> > > vvvint;
typedef vector<string> vstring;
typedef vector< vector<string> > vvstring;
typedef vector<char> vchar;
typedef vector< vector<char> > vvchar;
typedef vector<long double> vdouble;
typedef vector< vector<long double> > vvdouble;
typedef vector< vector< vector<long double> > > vvvdouble;
typedef pair<ll,ll> pint;
typedef vector<pint> vpint;
typedef vector<bool> vbool;

#define rep(i,n) for(ll i=0;i<n;i++)
#define repf(i,f,n) for(ll i=f;i<n;i++)
#define repr(i,n) for(ll i=n-1;i>=0;i--)
#define mp make_pair
#define mt make_tuple
#define pb push_back
#define pf push_front
#define fi first
#define se second
#define ALL(obj) (obj).begin(), (obj).end()
// #define LLONG_MAX 9223372036854775806
#define vmax(vec) *max_element(vec.begin(), vec.end())
#define vmin(vec) *min_element(vec.begin(), vec.end())
#define vsort(vec) sort(vec.begin(), vec.end())
#define vsortgr(vec) sort(vec.begin(), vec.end(), greater<ll>())
#define MOD 1000000007
// #define MOD 998244353
// #define MOD LLONG_MAX
const double PI=3.14159265358979323846;

template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }




int dy[]={0, 0, 1, -1};
int dx[]={1, -1, 0, 0,};




void printv(vint &v){
  for(auto e:v) cout<<e<<" ";
  cout<<endl;
}

template< int mod >
struct ModInt {
  int x;

  ModInt() : x(0) {}

  ModInt(int64_t y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}

  ModInt &operator+=(const ModInt &p) {
    if((x += p.x) >= mod) x -= mod;
    return *this;
  }

  ModInt &operator-=(const ModInt &p) {
    if((x += mod - p.x) >= mod) x -= mod;
    return *this;
  }

  ModInt &operator*=(const ModInt &p) {
    x = (int) (1LL * x * p.x % mod);
    return *this;
  }

  ModInt &operator/=(const ModInt &p) {
    *this *= p.inverse();
    return *this;
  }

  ModInt operator-() const { return ModInt(-x); }

  ModInt operator+(const ModInt &p) const { return ModInt(*this) += p; }

  ModInt operator-(const ModInt &p) const { return ModInt(*this) -= p; }

  ModInt operator*(const ModInt &p) const { return ModInt(*this) *= p; }

  ModInt operator/(const ModInt &p) const { return ModInt(*this) /= p; }

  bool operator==(const ModInt &p) const { return x == p.x; }

  bool operator!=(const ModInt &p) const { return x != p.x; }

  ModInt inverse() const {
    int a = x, b = mod, u = 1, v = 0, t;
    while(b > 0) {
      t = a / b;
      swap(a -= t * b, b);
      swap(u -= t * v, v);
    }
    return ModInt(u);
  }

  ModInt pow(int64_t n) const {
    ModInt ret(1), mul(x);
    while(n > 0) {
      if(n & 1) ret *= mul;
      mul *= mul;
      n >>= 1;
    }
    return ret;
  }

  friend ostream &operator<<(ostream &os, const ModInt &p) {
    return os << p.x;
  }

  friend istream &operator>>(istream &is, ModInt &a) {
    int64_t t;
    is >> t;
    a = ModInt< mod >(t);
    return (is);
  }

  static int get_mod() { return mod; }
};

using modint = ModInt< MOD >;

// 繰り返し二乗法
ll power(ll a, ll b){
  if(a==1)return a;
  // if(a==0)re
  ll res=1;
  while(b>0){
    if(b&1) res=res*a%MOD;
    a=a*a%MOD;
    b>>=1;
  }
  return res;
}

const int MAX=2100000;
 
ll fact[MAX], fact_inv[MAX];
 
void init_fact(ll n){
  fact[0]=1;
  // 階乗の計算
  rep(i, n) fact[i+1]=fact[i]*(i+1)%MOD;
  fact_inv[n]=power(fact[n], MOD-2);
  // 逆元の計算
  for(ll i=n-1;i>=0;i--) fact_inv[i]=fact_inv[i+1]*(i+1)%MOD;
}
 
ll comb(ll n, ll r){
  return (fact[n]*fact_inv[r])%MOD*fact_inv[n-r]%MOD;
}
 
ll perm(ll n, ll r){
  return (fact[n]*fact_inv[n-r])%MOD;
}

struct UnionFind {
  vector< int > data;
 
  UnionFind(int sz) {
    data.assign(sz, -1);
  }
 
  bool unite(int x, int y) {
    x = find(x), y = find(y);
    if(x == y) return (false);
    if(data[x] > data[y]) swap(x, y);
    data[x] += data[y];
    data[y] = x;
    return (true);
  }
 
  int find(int k) {
    if(data[k] < 0) return (k);
    return (data[k] = find(data[k]));
  }
 
  int size(int k) {
    return (-data[find(k)]);
  }
};

int main() {
  // cout<<fixed<<setprecision(10);

  ll n,k; cin>>n>>k;
  vint a(n); rep(i,n) cin>>a[i];
  vint pos,neg;
  ll nzero = 0;
  rep(i,n){
    if(a[i] == 0)nzero++;
    else if(a[i] < 0) neg.push_back(-a[i]);
    else pos.push_back(a[i]);
  }
  sort(ALL(pos));
  sort(ALL(neg));

  // cout<<nzero<<endl;
  // printv(pos);
  // printv(neg);

  auto isOK = [&](ll x){
    ll cnt = 0;
    if(x > 0){
      // -+ と zero
      cnt += nzero*(nzero-1)/2;
      cnt += nzero*(neg.size() + pos.size());
      cnt += neg.size()*pos.size();
      // cout<<"cnt "<<cnt<<" ";
      // --
      rep(i, (ll)(neg.size())-1){
        auto it = upper_bound(ALL(neg), x/neg[i] - (x%neg[i]==0));
        ll c = max(0ll, (it - neg.begin()) - i - 1);
        cnt += c;
      }
      // cout<<"cnt "<<cnt<<" ";
      rep(i, (ll)(pos.size())-1){
        auto it = upper_bound(ALL(pos), x/pos[i] - (x%pos[i]==0));
        ll c = max(0ll, (it - pos.begin()) - i - 1);
        cnt += c;
      }
      // cout<<"cnt "<<cnt<<" ";
    }else{
      x *= -1;
      rep(i, neg.size()){
        auto it = upper_bound(ALL(pos), x/neg[i]);
        ll c = pos.end() - it;
        cnt += c;
      }
      // cout<<"cnt "<<cnt<<" ";
    }

    // cout<<"cnt "<<cnt<<endl;
    // puts("");

    return cnt >= k;
  };

  ll left = -3e18;
  ll right = 3e18;

  while(right - left > 1){
    ll mid = (left+right)/2;
    // cout<<mid<<endl;
    if(isOK(mid)) right = mid;
    else left = mid;
  }

  cout<<left<<endl;
  
  // repf(i,-13, 45){
    // cout<<i<<" "<<(int)(isOK(i))<<endl;
    // cout<<i<<" ";
    // isOK(i);
    // puts("");
  // }

  // vint hoge;
  // rep(i, n-1){
  //   repf(j,i+1,n){
  //     hoge.push_back(a[i]*a[j]);
  //   }
  // }
  // sort(ALL(hoge));

  // rep(i,hoge.size()){
  //   cout<<i+1<<" "<<hoge[i]<<endl;
  // }

}



Measured memory_bytes: 3956